roster_received_cb: don't leak a ref to the roster
roster_received_cb: don't leak a ref to the roster

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