Bugfix for the Event Service

Bugfix in the mechanism of handling failed MP workers in the Event Service. This patch covers the case when a worker fails to transition from the event processing state into the finalization state after receiving "No more events" message from the range scatterer. The idea here is that instead of releasing a fixed number of workers (nprocs), the scatterer will keep releasing the workers until it gets a signal that all of them have finished.