Reduce log level for @ExceptionHandler failure

Issue: SPR-13932

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ExceptionHandlerExceptionResolver.java

@@ -367,8 +367,8 @@ public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExce
 			exceptionHandlerMethod.invokeAndHandle(webRequest, mavContainer, exception, handlerMethod);
 		}
 		catch (Exception invocationEx) {
-			if (logger.isErrorEnabled()) {
+			if (logger.isDebugEnabled()) {
-				logger.error("Failed to invoke @ExceptionHandler method: " + exceptionHandlerMethod, invocationEx);
+				logger.debug("Failed to invoke @ExceptionHandler method: " + exceptionHandlerMethod, invocationEx);
 			}
 			return null;
 		}