idmap: unify passdb *id_to_sid methods

idmap: unify passdb *id_to_sid methods

Instead of passing down gid or uid, a pointer to a unixid is now sent
down. This acts as an in-out variable so that the idmap functions can
correctly receive ID_TYPE_BOTH, filling in cache details correctly
rather than forcing the cache to store ID_TYPE_UID or ID_TYPE_GID.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=10720

Change-Id: I11409a0f498e61a3c0a6ae606dd7af1135e6b066
Pair-programmed-with: Andrew Bartlett <abarlet@samba.org>
Signed-off-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>