r10522: finally got the locking working on solaris10. This adds a read lock on

r10522: finally got the locking working on solaris10. This adds a read lock on
the transaction lock in tdb_traverse_read(). This prevents a pattern
of locks which triggers the deadlock detection code in solaris10. I
suspect solaris10 is trying to prevent lock starvation by granting
locks in the order they were requested, which makes it much easier to
produce deadlocks.
(This used to be commit 54203aacd138c30826d54c5d9b6cc8d6e9e270f8)