HADOOP-15994. Upgrade Jackson2 to 2.9.8. Contributed by lqjacklee.

(cherry picked from commit 3bb745df18669e2ae400dc0d1a37a81cdc270eb2)

hadoop-project/pom.xml

@@ -69,7 +69,7 @@
 
     <!-- jackson versions -->
     <jackson.version>1.9.13</jackson.version>
-    <jackson2.version>2.9.5</jackson2.version>
+    <jackson2.version>2.9.8</jackson2.version>
 
     <!-- httpcomponents versions -->
     <httpclient.version>4.5.2</httpclient.version>