fix doc.

Author: hfutatzhanghb

hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/async/TestRouterAsyncRPCMultipleDestinationMountTableResolver.java

@@ -55,7 +55,7 @@ public class TestRouterAsyncRPCMultipleDestinationMountTableResolver extends
   @BeforeClass
   public static void setUp() throws Exception {
 
-    // Build and start a federated cluster
+    // Build and start a federated cluster.
     cluster = new StateStoreDFSCluster(false, 3,
         MultipleDestinationMountTableResolver.class);
     Configuration routerConf =