YARN-7387: org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.TestIncreaseAllocationExpirer fails intermittently. Contributed by Jim Brennan (Jim_Brennan)

(cherry picked from commit b1e07d27cc1a26be4e5ebd1ab7b03ef15032bef0)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/TestIncreaseAllocationExpirer.java

@@ -209,6 +209,7 @@ public class TestIncreaseAllocationExpirer {
     Thread.sleep(10000);
     // Verify container size is 1G
     am1.allocate(null, null);
+    rm1.drainEvents();
     Assert.assertEquals(
         1 * GB, rm1.getResourceScheduler().getRMContainer(containerId2)
             .getAllocatedResource().getMemorySize());
@@ -433,6 +434,7 @@ public class TestIncreaseAllocationExpirer {
 
     am1.allocate(null, null);
 
+    rm1.drainEvents();
     Assert.assertEquals(
         2 * GB, rm1.getResourceScheduler().getRMContainer(containerId2)
             .getAllocatedResource().getMemorySize());