title: solr cloud - java.lang.NoClassDefFoundError: org/apache/lucene/analysis/util/TokenizerFactory
body: <p>When start solr cloud with external zookeeper cluster, got error:</p>
  
  <blockquote>
    <p>java.lang.NoClassDefFoundError: org/apache/lucene/analysis/util/TokenizerFactory</p>
  </blockquote>
  
  <p>I checked the configuration, but didn't found any error.</p>
  
  <p>The additional 3rd party jars are added at: <code>solr-6.2.0-cloud/server/lib/ext</code>, is that a problem ?</p>
  
  <p>What could possibly be the reason? thanks.</p>