Signal a job to stop.

• If the job is PENDING, it will immediately transition to DONE.
• If the job is RUNNING, then the job will interrupt its work and terminate.
• If the job is DONE, stop has no effect.

Note: this is an asynchronous operation and it may take some time before a RUNNING job transitions to DONE. In fact, a job may still succeed or fail after stop has been signalled. Users should monitor job status with get until the job is DONE.