Updates flow objects in the database.

def UpdateFlows(self,
                  client_id_flow_id_pairs,
                  pending_termination=db.Database.unchanged):
    """Updates flow objects in the database."""
    for client_id, flow_id in client_id_flow_id_pairs:
      try:
        self.UpdateFlow(
            client_id, flow_id, pending_termination=pending_termination)
      except db.UnknownFlowError:
        pass