ZOOKEEPER-3050: update to the newest version of Jetty

Change-Id: I1f63c471e59a1ed9d1cf58e721fedf47452acc6b

Author: Patrick Hunt <phunt@apache.org>

Reviewers: Michael Han <hanm@apache.org>

Closes #526 from phunt/ZOOKEEPER-3050

build.xml

@@ -51,7 +51,7 @@ xmlns:cs="antlib:com.puppycrawl.tools.checkstyle.ant">
 
     <property name="javacc.version" value="5.0"/>
 
-    <property name="jetty.version" value="9.2.18.v20160721"/>
+    <property name="jetty.version" value="9.4.10.v20180503"/>
     <property name="jackson-mapper-asl.version" value="1.9.11"/>
     <property name="dependency-check-ant.version" value="2.1.0"/>