modify domains integration test helper
modify domains integration test helper

- DefaultSharedDomain now guards against internal routes

Co-authored-by: Weyman Fung <4ab5e17be5c5cdce6cf54d6174afda06421ccec1@pivotal.io>
Co-authored-by: Merric de Launey <79964dcbacbf8006d1234555614dad3bcf49e6d6@pivotal.io>

cloudfoundry/cli,cloudfoundry/cli,cloudfoundry/cli