SimpleJobService stop/stopAll need to support JobOperator

[cppwfs]

Currently SimpleJobService sets the JobExecution to Stopping or Stopped. This signals that the batch job to stop on the next step, which is normal. However, it does not support stopping a Stoppable tasklet, which is a feature of the SimpleJobOperator.stop/stopAll methods .
SCDF needs to create a SCDFSimpleJobOperator that overrides the stop and stopAll methods so that it implements this feature. The reason SCDF can't use the existing SimpleJobOperator.stop/stopAll methods is that batch uses a MapJobRegistry to retrieve step information, which will not be in a consistent state within SCDF.

[cppwfs]

Closed via PR.