YARN-3623. Add a config to indicate the Timeline Service version. Contributed by Xuan Gong.

(cherry picked from commit f910e4f639dc311fcb257bfcb869b1aa8b2c0643)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/resources/yarn-default.xml

@@ -1887,7 +1887,7 @@
     <description>Indicate what is the current version of the running
     timeline service. For example, if "yarn.timeline-service.version" is 1.5,
     and "yarn.timeline-service.enabled" is true, it means the cluster will and
-    should bring up the timeline service v.1.5.
+    should bring up the timeline service v.1.5 (and nothing else).
     On the client side, if the client uses the same version of timeline service,
     it should succeed. If the client chooses to use a smaller version in spite of this,
     then depending on how robust the compatibility story is between versions,