Retrieve volume in update_migrated_volume

Retrieve volume in update_migrated_volume

When transferring db volume module through RPC call, it becomes
dict objects during RPC call. The attributes/properties
of the type can't be used.
As a result, to get volume['name'] raises KeyError.

The issue is fixed by retrieving volume from db.
Using volume version object will fix everything but it is
too late in Liberty. To keep code consistency, db.get_volume
is used in the fix.

Change-Id: I5ac7f083d5b4b7490347069728eb4b938c20885c
Closes-bug: 1491210