[Oglopf]

https://osc.github.io/ood-documentation-test/vnc-template-options/reference/files/submit-yml/vnc-bc-options.html

Documents three VNC batch connect options on the VNC options page:

• vncserver_cmd and vncpasswd_cmd, added in pin vncserver and vncpasswd to paths and adds vnc tests ood_core#1006. Sites can pin vncserver and vncpasswd to full paths, or set VNCSERVER_CMD / VNCPASSWD_CMD. The page notes that the variables have to be set before the VNC server starts (script_wrapper or job_environment), and that before.sh is too late. These options apply to the vnc template only.
• vnc_clean, which was listed in the YAML overview but never described. The entry explains when it runs, that the default now stops only this job's VNC server by display, how it behaves in vnc_container, and that an override replaces the default completely.

Also fixes the websockfiy_cmd typo in the websockify_cmd entry.

The vnc_clean entry describes the behavior from OSC/ood_core#1000, so this should merge after that PR.