Restart job: Validate in flows service that the current spark job has stopped before issuing a new start job instance

[rohit489]

Restart job: Validate in flows service that the current spark job has stopped before issuing a new start job instance.

Repro steps:

1. Restart a currently running job from the jobs page

Actual:
Sometimes the currently running job continues and a new instance of the same job get triggered

Expected:
Restart job api should validate that the currently running job instance has stopped before starting a new instance