Inconsistent jetty version because of dependabot updates

[rakeshramakrishnan]

Error while starting the distributed mode:

Exception in thread "main" java.lang.NoClassDefFoundError: org/eclipse/jetty/util/component/Graceful$Shutdown
	at org.eclipse.jetty.server.AbstractConnector.<init>(AbstractConnector.java:156)
	at org.eclipse.jetty.server.AbstractNetworkConnector.<init>(AbstractNetworkConnector.java:44)
	at org.eclipse.jetty.server.ServerConnector.<init>(ServerConnector.java:219)
	at org.eclipse.jetty.server.ServerConnector.<init>(ServerConnector.java:94)
	at org.eclipse.jetty.server.Server.<init>(Server.java:122)
	at org.apache.bookkeeper.stats.prometheus.PrometheusMetricsProvider.start(PrometheusMetricsProvider.java:103)
	at io.openmessaging.benchmark.Benchmark.main(Benchmark.java:139)
Caused by: java.lang.ClassNotFoundException: org.eclipse.jetty.util.component.Graceful$Shutdown
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

This commit seems to break the distributed mode because of jetty version mismatch: b163731

What's wrong: the commit has only updated jetty-server and not jetty-util

Fix: Update jetty-util in benchmark-framework/pom.xml to the same version as jetty-server: 9.4.17.v20190418

[aloknnikhil]

Thanks! Can you submit a PR?

[rakeshramakrishnan]

Here's the PR: #13