test(wsgi): Refactor tests in preparation for API v1.1

The tests were refactored into an inheritance model so that we can
share as much of the testing code as possible between v1.0 and v1.1.

As a part of this process, test class names were normalized and the
py3k check for keystone middleware was removed.

Change-Id: I04d342e2ce8bfd4fa0829935deb9b2753dd5af32
Partially-Implements: blueprint api-v1.1
Merge "test(wsgi): Refactor tests in preparation for API v1.1"