HDFS-16585.Add @VisibleForTesting in Dispatcher.java (#4337)

Co-authored-by: Ashutosh Gupta <ashugpt@amazon.com>

Reviewed-by: Tao Li <tomscut@apache.org>
Reviewed-by: Ayush Saxena <ayushsaxena@apache.org>
Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>
(cherry picked from commit bee538f785c012794a2dcf122dc8717b18beb0f0)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/Dispatcher.java

@@ -239,6 +239,7 @@ public class Dispatcher {
     private DDatanode proxySource;
     private StorageGroup target;
 
+    @VisibleForTesting
     PendingMove(Source source, StorageGroup target) {
       this.source = source;
       this.target = target;
@@ -280,6 +281,7 @@ public class Dispatcher {
     /**
      * @return true if the given block is good for the tentative move.
      */
+    @VisibleForTesting
     boolean markMovedIfGoodBlock(DBlock block, StorageType targetStorageType) {
       synchronized (block) {
         synchronized (movedBlocks) {
@@ -1357,6 +1359,7 @@ public class Dispatcher {
    * 2. the block does not have a replica/internalBlock on the target;
    * 3. doing the move does not reduce the number of racks that the block has
    */
+  @VisibleForTesting
   boolean isGoodBlockCandidate(StorageGroup source, StorageGroup target,
       StorageType targetStorageType, DBlock block) {
     if (source.equals(target)) {