PDI-12318 - NullPointerException running job with massive parallel Job/Transformation loads

Fix concurrency issue. Lists being modified for concurrent access. For parallel jobs they must be synchronized.
No junit test since it is difficult to mock calls for private methods. Integration tests will be time consuming since concurrent access to Lists related issues is hard to reproduce.

modified:   engine/src/org/pentaho/di/job/Job.java
Actually not so huge just because normally I assume it is a rare case when one job has more then 100 job entries executed in parallel. This lists is used only to store job entry result after execution. And the issue can be simulated for the case when all n parallel entries is end up in one moment, or all the parallel entries attempts to throw exception.

But that is correct - ConcurrentLinkedQueue will be faster then synchronized ArrayList in this case. That will be even more suitable since it is prohibit null elements.

Thank you for review.