[PATCH] device-mapper: Trigger an event when a table is deleted

If anything is waiting on a device's table when the device is removed, we
must first wake it up so it will release its reference.  Otherwise the
table's reference count will not drop to zero and the table will not get
removed.

Signed-Off-By: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>