Describe the bug
The TestClient.root_path attribute doesn't seem to apply the given prefix when making test requests.

To Reproduce
Define a TestClient fixture with an arbitrary root_path argument and run tests.

Additional context
I defined a client fixture as follows, since the project's top level Router has "/api" as a prefix:

@pytest.fixture()
def client(app: "Starlite") -> "Iterator[TestClient]":
    with TestClient(app=app, root_path="/api") as client:
        yield client

The prefix was not applied when running tests, however, after manually prefixing a test path with "/api", the resultant call was made to http://testserver.local/api/api/.... (double prefix)