ldb error handling changes

[tridge at samba.org]

Hi Matthias,

I've been having a look at your ldb error handling changes. The patch

 "ldb:ldb.c/"ldb_wait" - change "ldb_wait" slightly in order to introduce error messages"

doesn't look right to me. It removes the check for handle->state ==
LDB_ASYNC_DONE. I'm guessing you thought it was OK to remove this as
we check for that state earlier in the same function? The problem is
that the call to tevent_loop_once(ev) in the switch can change the
state of the handle. So I think we do need to re-check the state after
the tevent_loop_once() call.

Cheers, Tridge