Volume usage notifications in Cinder during Cinder volume migrations are
incorrect.
Part of a volume migration is creating a new volume on the destination
backend and during this process Cinder will issue volume usage
notifications "create.start" and "create.end" even though this is not a
user volume creation and is inconsistent with other temporary volume and
snapshot creation cases.
Also one of the latest steps during the volume creation is to delete one
of the 2 volumes (the source or the destination) and in that case Cinder
will only issue a "delete.end" notification without its corresponding
"delete.start".
Since temporary volumes (for backups or migrations) are not counted
towards quota usage they should also not issue volume usage
notifications.
This patch makes sure that we don't do notifications when creating or
deleting temporary migration volumes.
In both cases it checks the migration_status field to see if it starts
with 'target:'. For creation the migration_status is set in
_migrate_volume_generic method before making the RPC call, so the data
will be there from the start, before the manager flow starts.
Closes-Bug: #1922920
Change-Id: I7164d700ef56a29e5d4f707fd2340e621bd6f351
28d9bca7d6