Fix fragile tests

- Trying to fix test `StateMachineTests.testTimerTransition`
  by releasing latch after stateContexts list is updated. This
  is probably reason why assert failed for that list size.
- Again, fixes #36

spring-statemachine-core/src/test/java/org/springframework/statemachine/AbstractStateMachineTests.java

@@ -178,8 +178,8 @@ public abstract class AbstractStateMachineTests {
 			if (message != null) {
 				log.info(this);
 			}
-			onExecuteLatch.countDown();
 			stateContexts.add(context);
+			onExecuteLatch.countDown();
 		}
 	}