YARN-8970. Improve the debug message in CS#allocateContainerOnSingleNode. Contributed by Zhankun Tang.

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

@@ -1615,8 +1615,8 @@ public class CapacityScheduler extends
             .add(node.getUnallocatedResource(), node.getTotalKillableResources()),
         minimumAllocation) <= 0) {
       if (LOG.isDebugEnabled()) {
-        LOG.debug("This node or this node partition doesn't have available or"
-            + "killable resource");
+        LOG.debug("This node or node partition doesn't have available or" +
+            " preemptible resource");
       }
       return null;
     }