ipv[46]: do compat setsockopt for MCAST_{JOIN,LEAVE}_GROUP directly

direct parallel to the way these two are handled in the native
->setsockopt() instances - the helpers that do the real work
are already separated and can be reused as-is in this case.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2 files changed