Fix failing of unittests in one thread
Fix failing of unittests in one thread

With change of default driver, that is used for unittests one additional
method 'ensure_share' was not mocked, that caused problems running
unittests in one thread.

Change-Id: Iea08207bb6200c37f5608d222dccdfbdc509b234
Closes-Bug: #1358854

openstack/manila,jcsp/manila,sajuptpm/manila,NetApp/manila,weiting-chen/manila,scality/manila,scality/manila,bswartz/manila,bswartz/manila,openstack/manila,vponomaryov/manila,vponomaryov/manila,redhat-openstack/manila,weiting-chen/manila,redhat-openstack/manila,NetApp/manila,sajuptpm/manila,jcsp/manila