Remove obsolete machine ref in header

- No need to pass machine as ref in header
- Moved location of debug message of event queuing

spring-statemachine-core/src/main/java/org/springframework/statemachine/support/AbstractStateMachine.java

@@ -177,12 +177,6 @@ public abstract class AbstractStateMachine<S, E> extends LifecycleObjectSupport
 		if (isComplete() || !isRunning()) {
 			return false;
 		}
-		// TODO: machine header looks weird!
-		event = MessageBuilder.fromMessage(event).setHeader("machine", this).build();
-		if (log.isDebugEnabled()) {
-			log.debug("Queue event " + event);
-		}
-
 		boolean accepted = acceptEvent(event);
 		scheduleEventQueueProcessing();
 		return accepted;
@@ -260,6 +254,10 @@ public abstract class AbstractStateMachine<S, E> extends LifecycleObjectSupport
 			return true;
 		}
 
+		if (log.isDebugEnabled()) {
+			log.debug("Queue event " + event);
+		}
+
 		Message<E> defer = null;
 		for (Transition<S,E> transition : transitions) {
 			State<S,E> source = transition.getSource();