If the user has not yet clicked on "Yes, this is my computer", remove the cert after generating an assertion.
Update the remove email test to deal with "one time certs" when re-signing in with secondPrimaryEmail
Add a comment about why signing in to login.persona.org does not clear the cert.
Merge pull request #3840 from shane-tomlinson/remove-certs-after-assertion-generation

If the user has not yet clicked on "Yes, this is my computer", remove the cert after generating an assertion.

@fmarier said "I think it's ready as well." Merging.