idmap_hash: remember new domain sids in idmap_hash_sid_to_id()

idmap_hash: remember new domain sids in idmap_hash_sid_to_id()

This is similar to the checks in idmap_autorid_sid_to_id()
to check if a new mapping should be created.

This change means that idmap_hash_id_to_sid() can return mappings
for new domains learned in idmap_hash_sid_to_id().

Signed-off-by: Stefan Metzmacher <metze@samba.org>