Glance client don't check Identity validate when get schemas.
So when you exec "glance image-create" with invalid credentials in
glance-api.conf, it returns "unrecognized arguments: --foo".
It is difficult to debug such message.
This change makes invalid credentials error clear.
Change-Id: Ib641333cd8d51f459df70306a1eeda250ada5ca1
Closes-Bug: 1467719