fix race condition Job.run() with IJobChangeEvent.running() #271

The abbreviation check eventQueueThread.isEmpty() can become true before
all events processed. Need to have a lock before doing the check.

runtime/bundles/org.eclipse.core.jobs/src/org/eclipse/core/internal/jobs/JobListeners.java

@@ -61,7 +61,7 @@ void waitAndSendEvents(InternalJob job, boolean shouldSend) {
 		boolean send = shouldSend || job.eventQueueLock.isHeldByCurrentThread();
 		// Synchronize eventQueue to get a stable order of events across Threads.
 		// There is however no guarantee in which Thread the event is delivered.
-		while (!job.eventQueue.isEmpty()) {
+		while (true) {
 			if (getJobListenerTimeout() == 0) {
 				// backward compatibility mode for listeners that may deadlock
 				if (send) {