YARN-5862. TestDiskFailures.testLocalDirsFailures failed (Yufei Gu via Varun Saxena)

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

@@ -244,7 +244,9 @@ public class TestDiskFailures {
     for (int i = 0; i < 10; i++) {
       Iterator<RMNode> iter = yarnCluster.getResourceManager().getRMContext()
                               .getRMNodes().values().iterator();
-      if ((iter.next().getState() != NodeState.UNHEALTHY) == isHealthy) {
+      // RMNode # might be zero because of timing related issue.
+      if (iter.hasNext() &&
+          (iter.next().getState() != NodeState.UNHEALTHY) == isHealthy) {
         break;
       }
       // wait for the node health info to go to RM