Add explicit empty test for host to exit link test
Add explicit empty test for host to exit link test

Now that exit links are being tested with their host property rather
than their rel attribute, non-http hrefs have to be handled explicitly.

kalleth/static,tadast/static,kalleth/static,robinwhittleton/static,alphagov/static,robinwhittleton/static,tadast/static,alphagov/static,alphagov/static,robinwhittleton/static,tadast/static,robinwhittleton/static,kalleth/static,tadast/static,kalleth/static