ClientCnxn(1161) can't get the current zk server add, so that - Session 0x for server null, unexpected error

　　When zookeeper occur an unexpected error( Not SessionExpiredException, SessionTimeoutException and EndOfStreamException), ClientCnxn(1161) will log such as the formart "Session 0x for server null, unexpected error, closing socket connection and attempting reconnect ". The log at line 1161 in zookeeper-3.3.3
　　We found that, zookeeper use "((SocketChannel)sockKey.channel()).socket().getRemoteSocketAddress()" to get zookeeper addr. But,Sometimes, it logs "Session 0x for server null", you know, if log null, developer can't determine the current zookeeper addr that client is connected or connecting.
　　I add a method in Class SendThread:InetSocketAddress org.apache.zookeeper.ClientCnxn.SendThread.getCurrentZooKeeperAddr().

　　Here:
/**

• Returns the address to which the socket is connected.
• @return ip address of the remote side of the connection or null if not
• connected
  */
  @Override
  SocketAddress getRemoteSocketAddress() {
  // a lot could go wrong here, so rather than put in a bunch of code
  // to check for nulls all down the chain let's do it the simple
  // yet bulletproof way
  .....