instructorCourseAddInstructor: vulnerable to eventual consistency #2474

For Issue #2474

Registration email method now uses the previously created instructorAttributes instead of trying to query for the same thing. Manually tested on staging server to ensure that emails are still sent out correctly and the instructor can join the course properly.

p.s Somehow github lumped commits from my other branch together with this branch, but I already did another commit to remove those changes.
No, this is a setting by the java GAE to automatically launch the uploaded application in the browser after the upload is complete. This is always set on my eclipse, but I always remove it before committing.