Add consistency group tests to test_volume_rpcapi
Add consistency group tests to test_volume_rpcapi

test_volume_rpcapi was missing tests for RPC calls related to
consistency groups. This commit adds them.

Change-Id: I08a1337467742c8ce2b24c9382df537841bdbcb2

apporc/cinder,Paul-Ezell/cinder-1,Paul-Ezell/cinder-1,dims/cinder,mahak/cinder,eharney/cinder,Hybrid-Cloud/cinder,openstack/cinder,bswartz/cinder,phenoxim/cinder,Datera/cinder,cloudbase/cinder,eharney/cinder,Hybrid-Cloud/cinder,Datera/cinder,dims/cinder,phenoxim/cinder,bswartz/cinder,Nexenta/cinder,cloudbase/cinder,winndows/cinder,scottdangelo/RemoveVolumeMangerLocks,j-griffith/cinder,NetApp/cinder,j-griffith/cinder,NetApp/cinder,scottdangelo/RemoveVolumeMangerLocks,scality/cinder,openstack/cinder,apporc/cinder,Nexenta/cinder,ge0rgi/cinder,scality/cinder,mahak/cinder,winndows/cinder