idmap_autorid: Fix a race condition when acquiring ranges

idmap_autorid: Fix a race condition when acquiring ranges

Here we are in a transaction to create a range, but we already found
one to exist. We need to return the information about this range to the
caller, just as we do when actually allocating the range. This does not
hit us with current code, as we just have one idmap child. However, if
we parallelize that, two children might have found a domain to not exist
and call idmap_autorid_acquire_range simultaneously. One will create
the range, the other one will find it to already exist. The second child
will also have to pass the info up.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>