mgr/volumes: Fail subvolume removal if it's in progress

mgr/volumes: Fail subvolume removal if it's in progress

Removing an in-progress subvolume clone with force doesn't
remove the clone index (tracker). This results in the cloner
thread to stuck in loop trying to clone the deleted one.

This patch addresses the issue by not allowing the subvolume clone
to be removed if it's not complete/cancelled/failed even with force option.
It throws the error EAGAIN, asking the user to cancel the pending clone
and retry.

Fixes: https://tracker.ceph.com/issues/51707
Signed-off-by: Kotresh HR <khiremat@redhat.com>