CI: split out "samba-ad-dc-ntvfs[-py2]" test targets

CI: split out "samba-ad-dc-ntvfs[-py2]" test targets

Many AD tests currently use the "samba" target. Split out a new target
"samba-ad-dc-ntvfs" and have all tests that use the "ad_dc_ntvfs" env
use the new target. This should greatly speed up the runtime for the "samba"
target and avoid swapping.

This reduces the total CI time by ~ 55%, I got an autobuild and a gitlab
pipeline finished in just ~ 100 mins!

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

Signed-off-by: Ralph Boehme <slow@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Mon Feb 11 14:10:12 CET 2019 on sn-devel-144