linux-imx

dm thin metadata: delete btrees when releasing metadata snapshot

The device details and mapping trees were just being decremented
before.  Now btree_del() is called to do a deep delete.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org