idmap_ad: Restore querying SFU nss info

idmap_ad: Restore querying SFU nss info

With the last commit the getpwsid call did not look at the winbind
nss info parameter anymore. This restores it for the idmap ad backend
with slightly different semantics and configuration: We now have the
unix_primary_group and unix_nss_info domain-specific parameters for
idmap config. This enables overriding the Windows primary group with
the unix one.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Uri Simchoni <uri@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>