multicast group using a raw socket, then removing the interface on which
the group is found, and joining a multicast group using a udp socket,
then removing the interface on which the group is found. An if_disc
interface is used as the interface on which to attach.
NB: A panic currently results from running this regression test, so do
so with caution.
PR: 77665
Reported by: Gavin Atkinson <gavin dot atkinson at ury dot york dot ac dot uk>
Reported by: Brooks Davis <brooks at FreeBSD dot org>
