start Zookeeper client

zkClientStartup.scala

def initialize() {
  // Embedded server startup here (see part 2)
  // ...
  
  curatorFramework = 
    CuratorFrameworkFactory.newClient(
      connectString, sessionTimeoutSec*1000, 
      connectionTimeoutSec*1000, new RetryOneTime(1))
      
  curatorFramework.start()
  curatorFramework.getZookeeperClient.blockUntilConnectedOrTimedOut()
  
  if (!curatorFramework.isStarted) {
    throw new Exception(
      "Connection to Zookeeper timed out after " + connectionTimeoutSec + " seconds")
  }
  
  selectLeader()
}