Reduce log level to DEBUG when @Tels isn't present

The default set of TestExecutionListeners is sufficient in most
integration testing scenarios; however, the TestContextManager
nonetheless logs an INFO message if the @TestExecutionListeners
annotation is not present on an integration test class.

In order to avoid flooding the logs with messages about the absence of
@TestExecutionListeners, this commit reduces the log level for such
messages from INFO to DEBUG.

Issue: SPR-8645

spring-test/src/main/java/org/springframework/test/context/TestContextManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2012 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -181,8 +181,8 @@ private TestExecutionListener[] retrieveTestExecutionListeners(Class<?> clazz) {
 
 		// Use defaults?
 		if (declaringClass == null) {
-			if (logger.isInfoEnabled()) {
-				logger.info("@TestExecutionListeners is not present for class [" + clazz + "]: using defaults.");
+			if (logger.isDebugEnabled()) {
+				logger.debug("@TestExecutionListeners is not present for class [" + clazz + "]: using defaults.");
 			}
 			classesList.addAll(getDefaultTestExecutionListenerClasses());
 			defaultListeners = true;