Remove premature login cancel so post-login popup gets shown (Bug 105052...

This takes out the `oncancel()` call from login.js which tests for a dismissed window. We miight want to take out the whole `popup_interval`. This might be a problem, but I have heard the whole popup is going away in favour of a solution that is embedded in the page, which would be better in a variety of ways.
Thanks! Before we called `oncancel()` which fired a `login_cancel` event, that somewhere had a handler registered to remove the class that caused the spinner. Now we just remove the class without the other side effects of calling `oncancel()`.