tdb: fix locking error

tdb: fix locking error

54a51839ea65aa788b18fce8de0ae4f9ba63e4e7 "Make tdb transaction lock
recursive (samba version)" was broken: I "cleaned it up" and prevented
it from ever unlocking.

To see the problem:
	$ bin/tdbtorture -s 1248142523
	tdb_brlock failed (fd=3) at offset 8 rw_type=1 lck_type=14 len=1
	tdb_transaction_lock: failed to get transaction lock
	tdb_transaction_start failed: Resource deadlock avoided

My testcase relied on the *count* being correct, which it was.  Fixing that
now.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Michael Adam <obnox@samba.org>