fix comments

Author: tomscut

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java

@@ -1894,7 +1894,7 @@ public DatanodeCommand[] handleHeartbeat(DatanodeRegistration nodeReg,
    * @param failedVolumes count of failed volumes at DataNode
    * @param volumeFailureSummary info on failed volumes at DataNode
    * @param volumeUsageStdDev the standard deviation of volume usage
-   x
+   *
    * @throws IOException if there is an error
    */
   public void handleLifeline(DatanodeRegistration nodeReg,