HADOOP-17841. Remove ListenerHandle from Hadoop registry (#3278)

Author: virajjasani

hadoop-common-project/hadoop-registry/src/main/java/org/apache/hadoop/registry/client/impl/zk/CuratorService.java

@@ -824,9 +824,8 @@ protected String dumpRegistryRobustly(boolean verbose) {
  * Registers a listener to path related events.
  *
  * @param listener the listener.
- * @return a handle allowing for the management of the listener.
  */
- public ListenerHandle registerPathListener(final PathListener listener) {
+ public void registerPathListener(final PathListener listener) {
 
  CuratorCacheListener cacheListener = CuratorCacheListener.builder()
  .forCreatesAndChanges((oldNode, node) -> {
@@ -854,7 +853,6 @@ public ListenerHandle registerPathListener(final PathListener listener) {
  .build();
 
  curatorCacheBridge.listenable().addListener(cacheListener);
- return () -> curatorCacheBridge.listenable().removeListener(cacheListener);
  }
 
  // TODO: should caches be stopped and then restarted if need be?