Filter out google-rbc-announcement messages
Filter out google-rbc-announcement messages

They are server generated containing no interesting information
and appear in clients as if sent by peer

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=36647

mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,mlundblad/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble