Make remove_volume_connection() use objects

Changes the remove_volume_connection() method in compute manager
to take objects.

Related to blueprint compute-manager-objects-juno

Change-Id: I4fabee87df409accd947db3d5b429f7e871c2d60
Updated from global requirements

Change-Id: I51682a7a4b46a88598639c0e779857537dbc2e2c
Merge "Make remove_volume_connection() use objects"
Merge "Updated from global requirements"