Changeset 11082

#2153

• added a new method HandleStartStopPauseError in Executor to handle error conditions in the same way
• added timeouts for semaphores so that failed tasks or tasks with endless loops don't block the slave
• removed ExceptionOccured events from Executor/SlaveTask/TaskManager and use TaskFailed instead
• removed another ExcpetionOccured event in HeartbeatManager that was never used