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.
does the spinner get reverted upon popup dismissal? ([bug 1033698](https://bugzilla.mozilla.org/show_bug.cgi?id=1033698))