Setting up driver aliases for keystone domains

Issue: Starting from pike, keystone fails to initialize drivers
       by full path. Error from the log:
       ImportError: (u'Unable to find %(name)r driver in
       %(namespace)r.', {'namespace': 'keystone.identity', 'name':
       'keystone.identity.backends.ldap.Identity'})

Fix:   Use driver aliases taken from keystone egg entry_points.txt

Change-Id: I1dbf916741bd84d4a5e8963d0bfced2b786ac512
3 files changed