lib:socket: If returning early, set ifaces

lib:socket: If returning early, set ifaces

Prevents a segfault in load_interfaces() when total interfaces == 1.
Fixes regression caused by da68a1b2f417ec82ea4ed3e7a4d867cef8ca8f93.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13665

Signed-off-by: David Mulder <dmulder@suse.com>
Reviewed-by: Ralph Böhme <slow@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Sun Oct 28 00:35:35 CEST 2018 on sn-devel-144