s3:winbindd: use wb_sids2xids instead of wb_sid2uid in winbindd_sid_to_uid

s3:winbindd: use wb_sids2xids instead of wb_sid2uid in winbindd_sid_to_uid

The main purpose of the change is to hand the sid into the
idmap backend and handle responsiblity for handling the
sid-type correctly to the idmap backend instead of failing
directly when the sid is not of type user.

Hence backends like rid who are sid-type agnostic, can
return uids also for sids of other types. This is an important
fix to make sid_to_uid behave the consistently with and without
the presence of cache entries.

We need to additionally filter the result for id type UID
or more general (BOTH) to keep the behaviour.

This is a step towards using only one codepath to id_mapping.

Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>