lite ui ajax shows uninformative message when session is logged out with HTTP 302 response

If the user logged out of SLO or the session expires, and the user tries an ajax call, they get an error.

> We authenticate with CAS server and sessions expires after some time. This is no problem with the admin UI which will redirect you back to
> the login page to re-authenticate when you click on a link. However, this is not the case with the Lite UI, I will usually get a message box
> telling me that the XML request failed. If I re-authenticate using the Admin UI and go back in the Lite UI and do the same task, everything
> is back to normal. I believe this is because of the Ajax behind. It would be nice if there was a way to have a re-authentication (refresh
> the page maybe ? I think you need a new webrequest to have the app redirect you to the login page)
>
> Thanks
>
> Sébastien Gagné, | Analyste en informatique