HADOOP-16530. Update xercesImpl in branch-2.

Signed-off-by: Masatake Iwasaki <iwasakims@apache.org>

hadoop-project/pom.xml

@@ -1108,7 +1108,7 @@
       <dependency>
         <groupId>xerces</groupId>
         <artifactId>xercesImpl</artifactId>
-        <version>2.9.1</version>
+        <version>2.12.0</version>
       </dependency>
 
       <dependency>