Fix issue of volume after host-assisted migration

Fix issue of volume after host-assisted migration

In host-assisted migration, Cinder framework currently doesn't
update name_id and provider_location when the driver doesn't provide
name_id or provider_location in update_migrated_volume

This changes previous Cinder behavior which will update name_id and
provider_location anyway. Any operation against this volume will not
be successful; for example, volume deletion cannot delete it's
underlying LUN.

This fix will update name_id and provider_location if driver doesn't
return them.

Closes-Bug: #1487952
Change-Id: Ice72fc792f0ea8909c027e6df99cff9bbeef5e48