GabbleRoster: don't emit ContactsChanged for no-op changes, except subscription requests
GabbleRoster: don't emit ContactsChanged for no-op changes, except subscription requests

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