Revert "Adds certificate tests for keystone v3"

The tests caused technical issues on the stable/icheouse
gate with stable/havana -> stable/icehouse grenade/upgrade jobs.

Please resubmit the patch after the issue is resolved.

This reverts commit 1b560b239be149f8b8b3c99b723875a2c81ac85e.

Change-Id: I0ced519b68ef1e55a0f56af58a518d77f18b2adc
Merge branch 'master' of https://github.com/openstack/tempest