s3-libnet: avoid using lp_dns_hostname() in join code

s3-libnet: avoid using lp_dns_hostname() in join code

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15777

This codepath is also used for provisiong non-local machines into AD
during offlinejoin operations. When creating accounts for non-local
machines we certainly need to be able to use arbitrary hostname other
than lp_netbios_name() (which is used internally by lp_dns_hostname()).
This partly reverts 0e96092c1895ecb41d4064111566b4ada71fe457.

Guenther

Signed-off-by: Guenther Deschner <gd@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
Autobuild-User(master): Andreas Schneider <asn@cryptomilk.org>
Autobuild-Date(master): Thu Jan 30 07:35:05 UTC 2025 on atb-devel-224

(cherry picked from commit 062dc07e9b9c8e260548d0bca4d02819bdc60326)

Autobuild-User(v4-21-test): Jule Anger <janger@samba.org>
Autobuild-Date(v4-21-test): Wed Feb 12 10:37:56 UTC 2025 on atb-devel-224