Comment 6 for bug 1321303

So initial investigation indicates it's related to the workers sharing an EngineListener object, if you create the listener in the start() instead of the constructor the problem is solved.

That also highlights the problem that the workers are all creating StackWatch objects and starting periodic tasks on the parent TheadGroupManager object - I think that will result in a periodic watcher task being fired by a timer for every stack on every worker, which is not what we want.

Working on patches for both issues.