Set elapsed time for slave clients.

def set_elapsed_time(self, client):
        """Set elapsed time for slave clients."""
        related_clients = self.get_related_clients(client)
        for cl in related_clients:
            if cl.timer is not None:
                client.create_time_label()
                client.t0 = cl.t0
                client.timer.timeout.connect(client.show_time)
                client.timer.start(1000)
                break