Possible NPE while awaiting job execution termination

In org.jberet.runtime.JobExecutionImpl#awaitTermination, the variable jobTerminationLatch could still be null despite the null check, since this method is typically invoked by the batch client running in different thread than the main job execution thread. The variable jobTerminationLatch is accessed by the batch client thread, and is also updated by the main job execution thread at the end of job execution.

https://github.com/jberet/jsr352/blob/c0991d2c8b0471896956599428cbe1a90ef699f7/jberet-core/src/main/java/org/jberet/runtime/JobExecutionImpl.java#L137