selftest: Use a unique hostname/IP for the no_nss testenv

selftest: Use a unique hostname/IP for the no_nss testenv

The ad_dc_no_nss was re-using the ad_dc testenv but changing an
environment variable to disable the NSS wrapper module.

Presumably this would setup a second AD DC server with the same
hostname/IP as another DC (but with NSS disabled). This doesn't seem
like a good thing to be doing in the selftests. This patch changes
it so that the no_nss testenv uses a unique IP/hostname.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>