Keystone no longer has any special functionality hidden behind the admin
site. KEYSTONE_AUTH_URI which used to point to the admin site has long
ago been changed to be a copy of KEYSTONE_SERVICE_URI, which points to
the public site.
Drop all KEYSTONE_AUTH_* variables except KEYSTONE_AUTH_URI which may
still be in use in some plugins.
This also allows to finally drop the fixup_keystone() function.
Change-Id: I549f3cadc27d137e014241cdd47e90267859c848
c2491bac9d