mgr/volumes: Fix pool removal on volume deletion

mgr/volumes: Fix pool removal on volume deletion

While volume deletion, the associated pools are not always
removed. The pools are removed only if the volume is created
using mgr plugin and not if created with custom osd pools.
This is because mgr plugin generates pool names with specific
pattern. Both create and delete volume relies on it. This
patch fixes the issue by identifying the pools of the volume
without relying on the pattern.

Fixes: https://tracker.ceph.com/issues/45910
Signed-off-by: Kotresh HR <khiremat@redhat.com>