YARN-6284. hasAlreadyRun should be final in ResourceManager.StandByTransitionRunnable

(Contributed by Laura Adams via Daniel Templeton)

(cherry picked from commit 0a05c5c5989edeba2cffe16e80350245778cefce)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/ResourceManager.java

@@ -798,7 +798,7 @@ public class ResourceManager extends CompositeService implements Recoverable {
   private class StandByTransitionRunnable implements Runnable {
     // The atomic variable to make sure multiple threads with the same runnable
     // run only once.
-    private AtomicBoolean hasAlreadyRun = new AtomicBoolean(false);
+    private final AtomicBoolean hasAlreadyRun = new AtomicBoolean(false);
 
     @Override
     public void run() {