winbindd: fix predefined domains routing in find_lookup_domain_from_sid()

winbindd: fix predefined domains routing in find_lookup_domain_from_sid()

Route predefined domains through the BUILTIN domain child, not passdb.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12164

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Ralph Boehme <slow@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: David Mulder <dmulder@suse.com>
Reviewed-by: Andreas Schneider <asn@samba.org>
(cherry picked from commit b512a58bbd7361cbbcf68f6713943377338fc2a1)