listen for data and end on the response not the request

I had to do something during the meetings ;-). Anyways, this reworks check_primary_support to listen on right objects for certain events, and pulls the logic for checkResource into the end event handler of the request. Hope I didn't change what was intended to work (although did allow for using browserid.org instead of login.persona.org, although maybe I should back that out).

Fixes https://github.com/mozilla/browserid/issues/3221