Remove duplicated identity v2 clients

On the commit I3c09396f36a82d484de226cfe27848b6916cb636 , we kept
these clients intentionaly to avoid breaking the other gates.
Now we are ready to remove them by putting patches on
https://review.openstack.org/#/q/status:open+branch:master+topic:use-tempest-lib

Change-Id: I769e09771e28119a19d3462b233518ba5ae7426e
Depends-On: I74a5d5ed43f758b88a22ded293d85d046005d41f
3 files changed