Add keystone v3 support to client

All clients should support keystone v3 in kilo. This patch adds
support for keystone sessions, keystone endpoint discovery and support
for the CLI to provide keystone v3 options.

Bumps python-keystoneclient to >=0.11.1 to bring in session support.

This patch was previously dependent on a separate one to add session
support but that work has been squashed into this and its review
(https://review.openstack.org/#/c/131309) will be abandoned.

Co-Authored-By: David Hu <david.hu@hp.com>
Change-Id: I0f4931f1e6566a7b83280302f884248c8db909c5
Implements: blueprint support-keystone-v3
Merge "Add keystone v3 support to client"