Checks whether n-f nodes completed view change and whether one
        of them is the next primary

def _hasViewChangeQuorum(self):
        # This method should just be present for master instance.
        """
        Checks whether n-f nodes completed view change and whether one
        of them is the next primary
        """
        num_of_ready_nodes = len(self._view_change_done)
        diff = self.quorum - num_of_ready_nodes
        if diff > 0:
            logger.info('{} needs {} ViewChangeDone messages'.format(self, diff))
            return False

        logger.info("{} got view change quorum ({} >= {})".
                    format(self.name, num_of_ready_nodes, self.quorum))
        return True