gabble_roster_handle_add: track async errors
gabble_roster_handle_add: track async errors

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