test: Fix ceph_test_rados_watch_notify to delete the pools it creates

Fixes: #7934

Signed-off-by: David Zafman <dzafman@redhat.com>
Merge pull request #2459 from ceph/wip-7934

test: Fix ceph_test_rados_watch_notify to delete the pools it creates

Reviewed-by: Loic Dachary <loic-201408@dachary.org>