Enhance the function configured by execution.shutdown-on-attached-exit by heartbeat between client and dispatcher

If the param execution.shutdown-on-attached-exit is set to true, perform a best-effort cluster shutdown when the CLI is terminated abruptly.

But when the client is killed by 'kill -9', the cluster will not shutdown for that the signal can not be sent. We can enhance the behavior by building the heart beat between the client and the job. Once the job can not received any heartbeat from the client, the job cancel itself.