make installAsLevelPropagator transient

see apache#1140 (comment)

Author: mknet

log4j-jul/src/main/java/org/apache/logging/log4j/jul/Log4jBridgeHandler.java

@@ -93,7 +93,7 @@ public class Log4jBridgeHandler extends java.util.logging.Handler implements Con
 
     private boolean doDebugOutput = false;
     private String julSuffixToAppend = null;
-    private boolean installAsLevelPropagator = false;
+    private transient boolean installAsLevelPropagator = false;
 
     /**
      * Adds a new Log4jBridgeHandler instance to JUL's root logger.