Mentioned in issue #158 but repeating here since that was closed.

The vncserver script starts an Xvnc process, sets things up, and then exits.
Killing the Process that came from vncserver is useless since that process will
probably have already exited. The Xvnc process "leaks".

Either

1. Directly launch Xvnc and kill it later.

or

2. Use "vncserver -kill :$DISPLAY" to shut down the display.