Added keystone v3 support

This patch enables keystone v3 token auth and ec2 auth.
Also it enables keystone v3 support in tempest.
Tempest code should be reviewed.

Change-Id: I421c6c16216d7a0cc9902c7351d504359a600adf
Implements: blueprint multi-tenancy-enforcement
Merge "Added keystone v3 support"