HADOOP-15816. Upgrade Apache Zookeeper version due to security concerns. Contributed by Akira Ajisaka.

hadoop-project/pom.xml

@@ -86,7 +86,7 @@
     <protobuf.version>2.5.0</protobuf.version>
     <protoc.path>${env.HADOOP_PROTOC_PATH}</protoc.path>
 
-    <zookeeper.version>3.4.9</zookeeper.version>
+    <zookeeper.version>3.4.13</zookeeper.version>
     <curator.version>2.12.0</curator.version>
     <findbugs.version>3.0.0</findbugs.version>
     <spotbugs.version>3.1.0-RC1</spotbugs.version>