Save test_auth_token_middleware from unlimited recursion

For Python 2.6, BaseAuthTokenMiddlewareTest will be
equal to AdjustedBaseAuthTokenMiddlewareTest in
BaseAuthTokenMiddlewareTest.setUp thus leading to
infinite recursion.

Also, parent's setUp was incorrectly called by
BaseAuthTokenMiddlewareTest.setUp twice: at the beginning
and at the end of the function.

Change-Id: I63fce65866ef9d8aebe9eb60f7ceb17463de0989
Fixes: bug #1130200
Merge "Save test_auth_token_middleware from unlimited recursion"