YARN-6799. Remove the duplicated code in CGroupsHandlerImp.java. (Contributed by Weiyuan via Yufei Gu)

(cherry picked from commit 5ab21dfe9c8e14585db71e02bcb021a526507f98)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/CGroupsHandlerImpl.java

@@ -367,17 +367,6 @@ class CGroupsHandlerImpl implements CGroupsHandler {
     if (enableCGroupMount) {
       // We have a controller that needs to be mounted
       mountCGroupController(controller);
-    } else {
-      String controllerPath = getControllerPath(controller);
-
-      if (controllerPath == null) {
-        throw new ResourceHandlerException(
-            String.format("Controller %s not mounted."
-                + " You either need to mount it with %s"
-                + " or mount cgroups before launching Yarn",
-                controller.getName(), YarnConfiguration.
-                NM_LINUX_CONTAINER_CGROUPS_MOUNT));
-      }
     }
 
     // We are working with a pre-mounted contoller