winbindd: handling of SIDs without domain reference in wb_sids2xids_lookupsids_done()

winbindd: handling of SIDs without domain reference in wb_sids2xids_lookupsids_done()

This lets wb_sids2xids_lookupsids_done() deal with wp_lookupsids
returning UINT32_MAX as domain index for SIDs from unknown domains.

Call find_domain_from_sid_noinit() to search our list of known
domains. If a matching domain is found, use it's name, otherwise use the
empty string "". This needed to handle Samba DCs which always returns
sid_index UINT32_MAX for unknown SIDs, even from known domains.

Currently the wb_lookupsids adds these fake domains with an empty string
as domain name, but that's not the correct place to do it. We need the
domain name as it gets passed to the idmap child where the choise of
idmap backend is based on the domain name. This will possibly be changed
in the future to be based on domain SIDs, not the name.

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>