Distinguish between NoSuchJobException and 0 JobInstance of an existing job

JobOperator javadoc:
http://docs.oracle.com/javaee/7/api/javax/batch/operations/JobOperator.html

some methods (e.g., getJobInstanceCount throw NoSuchJobException when the job name passed in as param represents no such job in the repository. There could also be the case where the job of that name does exist, but there is 0 job instance.

The current JobOperatorImpl throws NoSuchJobException when no job instance is found for that jobName, which should be fixed to distinghish them.

There could be similar issues, to a lesser extent, in other method impls in JobOperatorImpl