YARN-7645. TestContainerResourceUsage#testUsageAfterAMRestartWithMultipleContainers is flakey with FairScheduler (rkanter)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/MockRM.java

@@ -1199,6 +1199,7 @@ public class MockRM extends ResourceManager {
     nm.nodeHeartbeat(true);
     ((AbstractYarnScheduler)rm.getResourceScheduler()).update();
     rm.drainEventsImplicitly();
+    nm.nodeHeartbeat(true);
     MockAM am = rm.sendAMLaunched(attempt.getAppAttemptId());
     rm.waitForState(attempt.getAppAttemptId(), RMAppAttemptState.LAUNCHED);
     return am;
@@ -1215,6 +1216,7 @@ public class MockRM extends ResourceManager {
     nm.nodeHeartbeat(true);
     ((AbstractYarnScheduler)rm.getResourceScheduler()).update();
     rm.drainEventsImplicitly();
+    nm.nodeHeartbeat(true);
     MockAM am = new MockAM(rm.getRMContext(), rm.masterService,
         attempt.getAppAttemptId());
     rm.waitForState(attempt.getAppAttemptId(), RMAppAttemptState.LAUNCHED);