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.
No. Not sure how we can have both. Given a choice between the reviewer window popping up and a stray spinner if someone starts to login and and decides not to, I'd take the stray spinner. Or we can cancel the spinner when the popup is loaded.