nova: Expose `use_serial` to UI

[nicolasbock]

Right now the use_serial switch is hidden in the raw view but it's useful enough to expose it in the UI.

[Itxaka]

May need to open a bug for the docs to be updated methinks

[nicolasbock]

@Itxaka oh, right, totally forgot about that :smile:

[nicolasbock]

Filed bsc#1021701.

[dirkmueller]

I'm totally not convinced that it should be exposed because;

• It requires novnc to be disabled
• It is completely unprotected
• Only one client can access the console at any time

Was therr any request for this being exposed?

[nicolasbock]

@dirkmueller Yes, someone asked me yesterday on #cloud if we could enable it. I figured I would just throw this out on GitHub since it was so straightforward to do :smile:. It sounds like we rather shouldn't do it though.

[nicolasbock]

@vuntz I have added the hints @dirkmueller provided. Is there a way to format the hints more like a list? I tried inserting html, but that didn't work.