Fix Persona workflow for Marketplace login

test_marketplace_login is failing because of changes to the Persona workflow. This pull request addresses some of those changes. I was able to successfully navigate through all of the persona screens last night, but today am blocked by Persona errors ("We are very sorry. The server is under extreme load!").  Also, when I was able to complete the Persona login I was returned to the Marketplace app but it never completed signing in.

I still wanted to submit a pull request with my fixes for the Persona workflow for now. When those other issues are addressed I will update the pull request.