Gate openstackclient on DevStack

A review in DevStack (https://review.openstack.org/#/c/69107/) switches
most of the keystone commands to use openstackclient in order to support
testing Identity v3 API calls.  OpenStackclient should gate against
at least one DevStack job.

Change-Id: Ie0736fd557313c15bd8fdb212f8f0779974de149
Merge "Gate openstackclient on DevStack"