cinder list shows multiple duplicate copies of each volume
cinder list shows multiple duplicate copies of each volume

This is due to get_local_volumes api changed from community, it always
cannot get local volume from db(empty list []), so driver attempts
to insert new volumes every time restarted or periodically sync.

Change-Id: I225394bfaff2229dbb93caa69e067154c608c15a
Closes-Bug: 1435121

openstack/powervc-driver,stackforge/powervc-driver,openstack/powervc-driver,stackforge/powervc-driver