text: Title: [BUG]How to set the ip address in the cluster mode
  Body: Setting:
  This is my first time using Mars and I face some problems maybe pretty easy for you.
  
  I am using mars as distributed computation engine. when i set the cluster mode as the doc said. I am confused about the ip address here:
  
  mars-worker -H <host_name> -p <worker_port> -s <supervisor_ip>:<supervisor_port>
  mars.new_session('http://<web_ip>:<web_port>')
  (from https://mars-project.readthedocs.io/zh_CN/latest/installation/deploy.html)
  
  Question:
  1. does the ip means external network ip address or internal network?
  2. I tried the external network ip address and it failed.
  3. when I use the internal network ip address, and I am using VSCode on my Mac and remote-develop on a Linux system, how to open the web browser of the Mars WebUI on my Mac with the Linux internal network ip address？
  