Fix sanic_endpoint_test working with redirects

Before fix, it raises error like:

```
tests/test_utils.py F

================================= FAILURES =================================
______________________________ test_redirect _______________________________

app = <sanic.sanic.Sanic object at 0x1045fda20>, method = 'get', uri = '/1', gather_request = True, debug = False
server_kwargs = {}, request_args = (), request_kwargs = {}
_collect_request = <function sanic_endpoint_test.<locals>._collect_request at 0x1045ec950>
_collect_response = <function sanic_endpoint_test.<locals>._collect_response at 0x1045ec7b8>

    def sanic_endpoint_test(app, method='get', uri='/', gather_request=True,
                            debug=False, server_kwargs={},
                            *request_args, **request_kwargs):
        results = []
        exceptions = []

        if gather_request:
            def _collect_request(request):
                results.append(request)
            app.request_middleware.appendleft(_collect_request)

        async def _collect_response(sanic, loop):
            try:
                response = await local_request(method, uri, *request_args,
                                               **request_kwargs)
                results.append(response)
            except Exception as e:
                exceptions.append(e)
            app.stop()

        app.run(host=HOST, debug=debug, port=PORT,
                after_start=_collect_response, **server_kwargs)

        if exceptions:
            raise ValueError("Exception during request: {}".format(exceptions))

        if gather_request:
            try:
>               request, response = results
E               ValueError: too many values to unpack (expected 2)

sanic/utils.py:47: ValueError

During handling of the above exception, another exception occurred:

utils_app = <sanic.sanic.Sanic object at 0x1045fda20>

    def test_redirect(utils_app):
        """Test sanic_endpoint_test is working for redirection"""
>       request, response = sanic_endpoint_test(utils_app, uri='/1')

tests/test_utils.py:33:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

app = <sanic.sanic.Sanic object at 0x1045fda20>, method = 'get', uri = '/1', gather_request = True, debug = False
server_kwargs = {}, request_args = (), request_kwargs = {}
_collect_request = <function sanic_endpoint_test.<locals>._collect_request at 0x1045ec950>
_collect_response = <function sanic_endpoint_test.<locals>._collect_response at 0x1045ec7b8>

    def sanic_endpoint_test(app, method='get', uri='/', gather_request=True,
                            debug=False, server_kwargs={},
                            *request_args, **request_kwargs):
        results = []
        exceptions = []

        if gather_request:
            def _collect_request(request):
                results.append(request)
            app.request_middleware.appendleft(_collect_request)

        async def _collect_response(sanic, loop):
            try:
                response = await local_request(method, uri, *request_args,
                                               **request_kwargs)
                results.append(response)
            except Exception as e:
                exceptions.append(e)
            app.stop()

        app.run(host=HOST, debug=debug, port=PORT,
                after_start=_collect_response, **server_kwargs)

        if exceptions:
            raise ValueError("Exception during request: {}".format(exceptions))

        if gather_request:
            try:
                request, response = results
                return request, response
            except:
                raise ValueError(
                    "Request and response object expected, got ({})".format(
>                       results))
E               ValueError: Request and response object expected, got ([{}, {}, {}, <ClientResponse(http://127.0.0.1:42101/3) [200 OK]>
E               <CIMultiDictProxy('Content-Type': 'text/plain; charset=utf-8', 'Content-Length': '2', 'Connection': 'keep-alive', 'Keep-Alive': 'timeout=1')>
E               ])

sanic/utils.py:52: ValueError
```

tests/test_redirect.py

@@ -0,0 +1,96 @@
+import pytest
+
+from sanic import Sanic
+from sanic.response import text, redirect
+from sanic.utils import sanic_endpoint_test
+
+
+@pytest.fixture
+def redirect_app():
+    app = Sanic('test_redirection')
+
+    @app.route('/redirect_init')
+    async def redirect_init(request):
+        return redirect("/redirect_target")
+
+    @app.route('/redirect_init_with_301')
+    async def redirect_init_with_301(request):
+        return redirect("/redirect_target", status=301)
+
+    @app.route('/redirect_target')
+    async def redirect_target(request):
+        return text('OK')
+
+    @app.route('/1')
+    def handler(request):
+        return redirect('/2')
+
+    @app.route('/2')
+    def handler(request):
+        return redirect('/3')
+
+    @app.route('/3')
+    def handler(request):
+        return text('OK')
+
+    return app
+
+
+def test_redirect_default_302(redirect_app):
+    """
+    We expect a 302 default status code and the headers to be set.
+    """
+    request, response = sanic_endpoint_test(
+        redirect_app, method="get",
+        uri="/redirect_init",
+        allow_redirects=False)
+
+    assert response.status == 302
+    assert response.headers["Location"] == "/redirect_target"
+    assert response.headers["Content-Type"] == 'text/html; charset=utf-8'
+
+
+def test_redirect_headers_none(redirect_app):
+    request, response = sanic_endpoint_test(
+        redirect_app, method="get",
+        uri="/redirect_init",
+        headers=None,
+        allow_redirects=False)
+
+    assert response.status == 302
+    assert response.headers["Location"] == "/redirect_target"
+
+
+def test_redirect_with_301(redirect_app):
+    """
+    Test redirection with a different status code.
+    """
+    request, response = sanic_endpoint_test(
+        redirect_app, method="get",
+        uri="/redirect_init_with_301",
+        allow_redirects=False)
+
+    assert response.status == 301
+    assert response.headers["Location"] == "/redirect_target"
+
+
+def test_get_then_redirect_follow_redirect(redirect_app):
+    """
+    With `allow_redirects` we expect a 200.
+    """
+    response = sanic_endpoint_test(
+        redirect_app, method="get",
+        uri="/redirect_init", gather_request=False,
+        allow_redirects=True)
+
+    assert response.status == 200
+    assert response.text == 'OK'
+
+
+def test_chained_redirect(redirect_app):
+    """Test sanic_endpoint_test is working for redirection"""
+    request, response = sanic_endpoint_test(redirect_app, uri='/1')
+    assert request.url.endswith('/1')
+    assert response.status == 200
+    assert response.text == 'OK'
+    assert response.url.endswith('/3')