This adds additional test coverage to HostAuthorization to validate that
its behavior conforms to Rack SPEC.

This fixes the following two issues in the reponse returned by
DebugLocks:
- Rack::Lint::Error: uppercase character in header name
  Content-{Type/Length}
- Rack::Lint::Error: a header value must be a String or Array of
  Strings, but the value of 'content-length' is an Integer