Fix Authentication problem with Keystone V3
Fix Authentication problem with Keystone V3

Endpoint arg was missing when creating a Keystone client, and
authenticate() method had to be used as it's now lazy authn

Change-Id: Iaab491a8d7ea43814ac19b245e3dfdd886a978b3
Closes-Bug: #1271959

frossigneux/blazar,ChameleonCloud/blazar,openstack/blazar,stackforge/blazar,stackforge/blazar,frossigneux/blazar,ChameleonCloud/blazar,paramite/blazar,paramite/blazar,openstack/blazar,frossigneux/blazar