Fixed spec/requests/ authentication specs

- Update session_store to use :memory instead of default cookie_store for tests,
eliminating the 4K limit that was giving us the 500's.
- Needed to specify HTTP_USER_AGENT for a couple of tests in auth_spec.rb
PR Review Updates

- Simplified check in session_store initializer
- Reverting auth_specs tests as earlier.
- Updating request_referer_service.rb to handle empty referer
Merge pull request #1116 from abellotti/auth_specs

Fixed spec/requests/ authentication specs