gadolinium now uses udp2log multicast relay.

- gadolinium udp2log now consumes from multicast relay (from oxygen).
- Removing gadolinium as udp2log destination on frontend caches.
  This requires deploying squid changes as well.  Patch is at
  fenari:/home/otto/frontend.conf.php.rt.4720-2.patch

RT 4720

Change-Id: If7950b54912d128e3c93efa243d882dd2b37d723