update test to work with vouch refactor + some cleanup

The new vouch refactor is scheduled to land on production this week. This pull request updates provides updates to `def test_private_groups_field_as_public_when_logged_in()` in preparation for the deploy.

Note: once this is merged this test will fail on prod. This is OK, the current workflow of the project is to have tests updated to pass on mozillians-dev.allizom.org and mozillians.allizom.org. Once the prod deploy occurs prod will pass again.