Fixed RecetBadCertService call

The extension wasn't working in my setup (Firefox 23.0 on Linux).

There was a naming change in FF20 for RecentBadCertService:
https://developer.mozilla.org/en-US/docs/Updating_addons_broken_by_private_browsing_changes

I adjusted the code with the same approach in:
https://github.com/mk-fg/convergence/blob/master/client/chrome/content/CertificateStatus.js#L34