fix for keystone.user_present

----------
          ID: glance_user
    Function: keystone.user_present
        Name: glance
      Result: False
     Comment: An exception occurred in this state: Traceback (most recent call last):
                File "/usr/lib/pymodules/python2.7/salt/state.py", line 1371, in call
                  **cdata['kwargs'])
                File "/var/cache/salt/minion/extmods/states/keystone.py", line 189, in user_present
                  **connection_args)
                File "/var/cache/salt/minion/extmods/modules/keystone.py", line 884, in user_role_add
                  **connection_args).keys()[0]['name']
              TypeError: string indices must be integers, not str


This error will occur when a new user is being added and then subsequently user role is added.
It does not occur when an existing user is being updated and new roles added.