KAFKA-18831 Migrating to log4j2 introduce behavior changes of adjusti…

…ng level dynamically (#18969)

fix the following behavior changes.

1) in log4j 1, users can't change the logger by parent if the logger is declared by properties explicitly. For example, `org.apache.kafka.controller` has level explicitly in the properties. Hence, we can't use "org.apache.kafka=INFO" to change the level of `org.apache.kafka.controller` to INFO. By contrast, log4j2 allows us to change all child loggers by the parent logger.

2) in log4j2, we can change the level of root to impact all loggers' level. By contrast, log4j 1 can't. 

Reviewers: Chia-Ping Tsai <chia7712@gmail.com>

core/src/main/scala/kafka/utils/LoggingController.scala

@@ -112,24 +112,25 @@ private class Log4jCoreController extends LoggingControllerDelegate {
     val level = Level.toLevel(logLevel.toUpperCase(Locale.ROOT))
 
     if (loggerName == ROOT_LOGGER) {
-      Configurator.setAllLevels(LogManager.ROOT_LOGGER_NAME, level)
+      Configurator.setLevel(LogManager.ROOT_LOGGER_NAME, level)
       true
     } else {
       if (loggerExists(loggerName) && level != null) {
-        Configurator.setAllLevels(loggerName, level)
+        Configurator.setLevel(loggerName, level)
         true
       }
       else false
     }
   }
 
   override def unsetLogLevel(loggerName: String): Boolean = {
+    val nullLevel: Level = null
     if (loggerName == ROOT_LOGGER) {
-      Configurator.setAllLevels(LogManager.ROOT_LOGGER_NAME, null)
+      Configurator.setLevel(LogManager.ROOT_LOGGER_NAME, nullLevel)
       true
     } else {
       if (loggerExists(loggerName)) {
-        Configurator.setAllLevels(loggerName, null)
+        Configurator.setLevel(loggerName, nullLevel)
         true
       }
       else false