netlogon: Forward GetDCNameEx2 to winbind via IRPC

netlogon: Forward GetDCNameEx2 to winbind via IRPC

Here we simply forward everything without alteration (the same struct is
returned). This helps us to fix the case where the DC does not exist in
the target site, furthermore, this is supposed to work for trusted
domains.

In calling out to winbind, we now also notice if you provide a site
which exists in multiple domains and provide the correct domain (instead
of accidentally returning ourselves).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13365

Signed-off-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>