selftest:Samba3: use the correct NSS_WRAPPER_HOSTNAME

selftest:Samba3: use the correct NSS_WRAPPER_HOSTNAME

The value of NSS_WRAPPER_HOSTNAME needs to match value
we put into the NSS_WRAPPER_HOSTS file.

We had a mismatch of
idmapridmember.samba.example.com
vs.
idmapridmember.addom.samba.example.com

This causes getaddrinfo() in nss_wrapper to fallback to
the libc version, which talks to a dns server.
It's not clear if recent glibc code will reach resolve/socket wrapper.
So it's not unlikely that idmapridmember.samba.example.com will
be passed via the internet, which causes delays up to 20 seconds.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15355

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed Apr 12 20:29:05 UTC 2023 on atb-devel-224