Flushes the flow/hunt and all its requests to the data_store.

def Flush(self):
    """Flushes the flow/hunt and all its requests to the data_store."""
    self._CheckLeaseAndFlush()
    self.Load()
    super(FlowBase, self).Flush()
    # Writing the messages queued in the queue_manager of the runner always has
    # to be the last thing that happens or we will have a race condition.
    self.FlushMessages()