Add python-barbicanclient

Add python-barbicanclient, so that barbican can be
used by other openstack projects.  Specifically,
it is needed by nova and cinder for patches
https://review.openstack.org/#/c/104001/ and
https://review.openstack.org/#/c/104339/
to support cinder volume encryption using barbican
as the key manager.

Change-Id: I319f6cc834fb615f0a1c5aa22fabfbcff66ea771
Merge "Add python-barbicanclient"