Load foreman config in katello:reset rake task

The rake task katello:reset was failing during seeding, because
the admin user being created didn't have an email address.

This was because the foreman config settings weren't being loaded
before running db:seed.

I also added a test indicating that email is a required attribute.
Merge pull request #3537 from mkelley33/seed-admin-email

Add email for admin user to seeds