net: fix the order of DC lookup methods when joining a domain

net: fix the order of DC lookup methods when joining a domain

The dsgetdcname() function is able to try just DNS lookup, just NetBIOS,
or start with DNS and fall back to NetBIOS. For "net ads join", we know
most of the time whether the name of the domain we're joining is a DNS
name or a NetBIOS name. In that case, it makes no sense to try both lookup
methods, especially that DNS may fail and we want to fall back from site-aware
DNS lookup to site-less DNS lookup, with no NetBIOS lookup in between.

This change lets "net ads join" tell libnet what is the type of the domain
name, if it is known.

Signed-off-by: Uri Simchoni <urisimchoni@gmail.com>
Reviewed-by: Volker Lendecke <Volker.Lendecke@SerNet.DE>
Reviewed-by: Jeremy Allison <jra@samba.org>