Run example fails via PushStaged mode

[r4ntix]

Describe the bug
I start the scheduler and executor service in localhost:

./target/debug/ballista-scheduler -s push-staged --log-level-setting INFO,ballista_scheduler=DEBUG

./target/debug/ballista-executor -c 4 -s push-staged --log-level-setting INFO,ballista_executor=DEBUG

And run examples/src/bin/sql.rs, the executor was an error:

2022-09-14T07:18:35.502374Z ERROR tokio-runtime-worker ThreadId(08) ballista_executor::executor_server: Fail to connect to scheduler scheduler_ballista_localhost_50050 due to TonicError(tonic::transport::Error(Transport, hyper::Error(Connect, ConnectError("dns error", Custom { kind: Uncategorized, error: "failed to lookup address information: nodename nor servname provided, or not known" }))))

The executor can't connect to scheduler via scheduler_ballista_localhost_50050.

To Reproduce

The scheduler send scheduler_id in LaunchTaskParams to executor when launch task:
https://github.com/apache/arrow-ballista/blob/2e1f5d619760d3b7acce225a166a9507f9efe9a1/ballista/rust/scheduler/src/state/task_manager.rs#L415-L430

The scheduler_id generate by scheduler when start service, and value is format!("scheduler_{}_{}_{}", namespace, external_host, port):
https://github.com/apache/arrow-ballista/blob/2e1f5d619760d3b7acce225a166a9507f9efe9a1/ballista/rust/scheduler/src/main.rs#L171

In the process of the executor reporting the task status, call get_scheduler_client pass scheduler_id:
https://github.com/apache/arrow-ballista/blob/2e1f5d619760d3b7acce225a166a9507f9efe9a1/ballista/rust/executor/src/executor_server.rs#L507-L519

The scheduler_id value is format!("scheduler_{}_{}_{}", namespace, external_host, port), that can't lookup address via dns:
https://github.com/apache/arrow-ballista/blob/2e1f5d619760d3b7acce225a166a9507f9efe9a1/ballista/rust/executor/src/executor_server.rs#L222-L237

So the executor throw an error, and task fail.

Describe the solution you'd like
Fix scheduler_name to format!("{}:{}", opt.external_host, opt.bind_port), default is localhost:50050.
The prefix name of the log file remains format!("scheduler_{}_{}_{}", namespace, external_host, port).

[r4ntix]

@yahoNanJing

[yahoNanJing]

Thanks @r4ntix for finding out this issue. Could you help propose a PR for this fix?