YARN-10651. CapacityScheduler crashed with NPE in AbstractYarnScheduler.updateNodeResource(). Contributed by Haibo Chen

(cherry picked from commit f348ab3f2f468751af329a1ffce4917cb000fcbf)
(cherry picked from commit be6e99963ded94adf6f447ff53f2ba66b99120ca)
(cherry picked from commit 6863a5bb8ace591de3374102920bba916dbebfda)
(cherry picked from commit eb6c08e423dd06bf37ff44665ffb98c97e26ad08)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/AbstractYarnScheduler.java

@@ -805,6 +805,11 @@ public abstract class AbstractYarnScheduler
     try {
       writeLock.lock();
       SchedulerNode node = getSchedulerNode(nm.getNodeID());
+      if (node == null) {
+        LOG.info("Node: " + nm.getNodeID() + " has already been taken out of " +
+            "scheduling. Skip updating its resource");
+        return;
+      }
       Resource newResource = resourceOption.getResource();
       Resource oldResource = node.getTotalResource();
       if (!oldResource.equals(newResource)) {