Fix check_primary_support to give nicer failures for BID properties

[jbonacci]

This is what I see right now:
$ scripts/check_primary_support browserid.org
info: process type is check_primary_support
debug: missing required key: authentication
error: missing required key: authentication

$ scripts/check_primary_support diresworb.org
info: process type is check_primary_support
debug: missing required key: authentication
error: missing required key: authentication

$ scripts/check_primary_support https://diresworb.org
info: process type is check_primary_support
debug: https://diresworb.org is not a browserid primary: Error: getaddrinfo ENOENT

$ scripts/check_primary_support https://browserid.org
info: process type is check_primary_support
debug: https://browserid.org is not a browserid primary: Error: getaddrinfo ENOENT

Compare that to an external email domain:
$ scripts/check_primary_support gmail.com
info: process type is check_primary_support
debug: gmail.com is not a browserid primary - non-200 response code to /.well-known/browserid

and to one of our other properties which does support BID:
$ scripts/check_primary_support developer.mozilla.org
info: process type is check_primary_support
debug: developer.mozilla.org is not a browserid primary - non-200 response code to /.well-known/browserid

[callahad]

Closing as wontfix -- feel free to revert if you feel strongly.