Use cached db object in volume_mig_status ext

There is no need to rerequest the volume object from the db in
the extension because we already have a cached copy in the request.
This can potentially save hundreds of db queries in list.

Change-Id: I46da8c7b6c2af2435d246ebd8e95d4712065f1e7
Resolves-bug: 1308255
Merge "Use cached db object in volume_mig_status ext"