To really be sure about this, we could setDAGScheduler(this) within the preStart() hook of eventProcessActor.  During actor restart, the default implementation of postRestart() will call preStart(), but: 1) After this PR we're not restarting the eventProcessActor anyway; 2) Re-running setDAGScheduler should just reset the TaskScheduler's reference back to the same DAGScheduler instance (i.e., this.)