Change Server API

* Rename ServerStatus to ServerState internally

* Rename terminate to shutdown internally

* Update Scheduler API to match Server API

subscriber.go

@@ -43,7 +43,7 @@ func newSubscriber(params subscriberParams) *subscriber {
 	}
 }
 
-func (s *subscriber) terminate() {
+func (s *subscriber) shutdown() {
 	s.logger.Debug("Subscriber shutting down...")
 	// Signal the subscriber goroutine to stop.
 	s.done <- struct{}{}