v2.0 of the keystone API was deprecated in icehouse-2, moving to support v3 by default. This also fixes a bug in Horizon where if you specify v3 for the API version and v2.0 is still the auth url, login fails. Implements blueprint keystone-v3-default Partial-bug: #1267636 Change-Id: Ibc4872f24125fa74230eab781b002dffdba5f5da