Adding new whitehall test for non-auth http

Previously, all http was authenticated by default, even
www.*.alphagov.co.uk - and this is desirable in preview only. A
new whitehall-only case has been implemented to explicitly ensure
AUTH_USERNAME and AUTH_PASSWORD are uninstantiated.
including govuk_setenv to smokey
adding new Rake test to avoid EFG

Skyscape preview does not have EFG (we left it in EC2 for now)