Why calling reboot in SSH session hangs the terminal?

Issue

• The SSH sessions do not automatically close when a users executes reboot command.

• The user have to wait for it to kill itself with a broken pipe, or close the terminal completely.

  # init 6
  PolicyKit daemon disconnected from the bus.
  We are no longer a registered authentication agent.
  Write failed: Broken pipe
  

• Powering off remote node hangs ssh session on client end.