private ZookeeperServerConfig.Server.Builder newServer(int id, String hostName, boolean retired) {
        ZookeeperServerConfig.Server.Builder builder = new ZookeeperServerConfig.Server.Builder();
        builder.id(id);
        builder.hostname(hostName);
        builder.retired(retired);
        return builder;
    }
Tests dynamic reconfiguration of zookeeper cluster.

@author hmusum
zookeeper-server/zookeeper-server-common/src/test/java/com/yahoo/vespa/zookeeper/ReconfigurerTest.java