YARN-5922. Remove direct references of HBaseTimelineWriter/Reader in core ATS classes. Contributed by Haibo Chen.

(cherry picked from commit a5a55a54ab1568e941062ea3dabdd237f71f15c4)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/conf/YarnConfiguration.java

@@ -2112,8 +2112,8 @@ public class YarnConfiguration extends Configuration {
       TIMELINE_SERVICE_PREFIX + "reader.class";
 
   public static final String DEFAULT_TIMELINE_SERVICE_READER_CLASS =
-      "org.apache.hadoop.yarn.server.timelineservice" +
-          ".storage.HBaseTimelineReaderImpl";
+      "org.apache.hadoop.yarn.server.timelineservice.storage" + 
+          ".HBaseTimelineReaderImpl";
 
   /**
    * default schema prefix for hbase tables.