YARN-4566. Fix test failure in TestMiniYarnClusterNodeUtilization. (Takashi Ohnishi via rohithsharmaks)

(cherry picked from commit e0b14f26f5201a149218276469434df511697acc)

Conflicts:

	hadoop-yarn-project/CHANGES.txt

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-tests/src/test/java/org/apache/hadoop/yarn/server/TestMiniYarnClusterNodeUtilization.java

@@ -214,8 +214,10 @@ public class TestMiniYarnClusterNodeUtilization {
     // We check if the nodeUtilization is up to date
     for (int i=0; i<100; i++) {
       for (RMNode ni : rmContext.getRMNodes().values()) {
-        if (ni.getNodeUtilization().equals(nodeUtilization)) {
-          break;
+        if (ni.getNodeUtilization() != null) {
+            if (ni.getNodeUtilization().equals(nodeUtilization)) {
+              break;
+            }
         }
       }
       Thread.sleep(100);