build: Require --without-ad-dc for --without-ads

Building an AD DC while setting --without-ads makes no sense and just wastes compile time on our build hosts.

To allow samba-nt4 to build --without-ad-dc we set rpc.spoolss.notify
(which is built on the NTVFS fileserver for the callbacks) to run in
the ad_member environment rather than nt4_dc and ad_dc.

This is also just more realistic in any case.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>