Update zookeeper 3.5.x version to 3.5.9 (#1877)

Co-authored-by: Ed Coleman etcoleman <edcoleman@apache.org>
diff --git a/pom.xml b/pom.xml
index 3a6387a..60eab04 100644
--- a/pom.xml
+++ b/pom.xml
@@ -159,7 +159,7 @@
     <thrift.version>0.12.0</thrift.version>
     <unitTestMemSize>-Xmx1G</unitTestMemSize>
     <!-- ZooKeeper version -->
-    <zookeeper.version>3.5.8</zookeeper.version>
+    <zookeeper.version>3.5.9</zookeeper.version>
   </properties>
   <dependencyManagement>
     <dependencies>