offer-muc-stream-tube-ibb: remove commented code and explain why we can't catch NewChannel signal anymore
offer-muc-stream-tube-ibb: remove commented code and explain why we can't catch NewChannel signal anymore

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