YARN-6231. FairSchedulerTestBase helper methods should call scheduler.update to avoid flakiness. (kasha)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FairSchedulerTestBase.java

@@ -190,6 +190,7 @@ public class FairSchedulerTestBase {
 
     scheduler.allocate(id, ask, new ArrayList<ContainerId>(),
         null, null, NULL_UPDATE_REQUESTS);
+    scheduler.update();
     return id;
   }
   
@@ -240,6 +241,7 @@ public class FairSchedulerTestBase {
     ask.add(request);
     scheduler.allocate(attId, ask,  new ArrayList<ContainerId>(),
         null, null, NULL_UPDATE_REQUESTS);
+    scheduler.update();
   }
 
   protected void createApplicationWithAMResource(ApplicationAttemptId attId,