Stub authentication requests rather than plugins
Stub authentication requests rather than plugins

Rather than testing that a certain plugin was loaded test to make sure
that the client actually did the authentication request and that the
content of that request was correct.

This means we are not so tightly bound to those specific plugins and
this can be changed in later reviews.

Change-Id: Ia3ae0069e3e0277d655f0e251196eca658f94c75

klmitch/python-glanceclient,varunarya10/python-glanceclient,mmasaki/python-glanceclient,klmitch/python-glanceclient,JioCloud/python-glanceclient,varunarya10/python-glanceclient,JioCloud/python-glanceclient,mmasaki/python-glanceclient,openstack/python-glanceclient,openstack/python-glanceclient