YARN-10813. Set default capacity of root for node labels. Contributed by Andras Gyori

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

@@ -697,10 +697,11 @@ public class CapacitySchedulerConfiguration extends ReservationSchedulerConfigur
       // root.From AbstractCSQueue, absolute resource will be parsed and
       // updated. Once nodes are added/removed in cluster, capacity in
       // percentage will also be re-calculated.
-      return defaultValue;
+      return queue.equals("root") ? 100.0f : defaultValue;
     }
 
-    float capacity = getFloat(capacityPropertyName, defaultValue);
+    float capacity = queue.equals("root") ? 100.0f
+        : getFloat(capacityPropertyName, defaultValue);
     if (capacity < MINIMUM_CAPACITY_VALUE
         || capacity > MAXIMUM_CAPACITY_VALUE) {
       throw new IllegalArgumentException("Illegal capacity of " + capacity