'If the given ``state_changes`` differ from those last acknowledged by
the control service, send them to the control service.
:param state_changes: State to send to the control service.
:type state_changes: tuple of IClusterStateChange'

def _maybe_send_state_to_control_service(self, state_changes):

    if (self._last_acknowledged_state != state_changes):
        return self._send_state_to_control_service(state_changes)
    else:
        return succeed(None)
