Remove state altering in live-migration code
Remove state altering in live-migration code

 * Stops live migration from checking volume node because it
   will not be accessible if volumes are a separate service
 * Stops state modification of volumes during live migration
   because the volumes are not migrating
 * Partially implements blueprint volume-decoupling

Change-Id: I07bdbc660ff220e2079e643a002c4c6bb5df6db7

citrix-openstack-build/oslo.versionedobjects,openstack/oslo.versionedobjects