Manage existing: fix volume object saving
Manage existing: fix volume object saving

This needs an update to work with volume objects.

Currently, manage existing can fail here.

Change-Id: I9197220be201cbbb1cd8266ebb58b57641fc216f
Closes-Bug: #1518050

cloudbase/cinder,scality/cinder,dims/cinder,bswartz/cinder,openstack/cinder,eharney/cinder,Datera/cinder,cloudbase/cinder,NetApp/cinder,mahak/cinder,ge0rgi/cinder,scality/cinder,apporc/cinder,Hybrid-Cloud/cinder,apporc/cinder,phenoxim/cinder,Datera/cinder,Nexenta/cinder,openstack/cinder,j-griffith/cinder,eharney/cinder,NetApp/cinder,j-griffith/cinder,Nexenta/cinder,dims/cinder,mahak/cinder,bswartz/cinder,Hybrid-Cloud/cinder,phenoxim/cinder