test: use reserved invalid hostname for tests

PR-URL: https://github.com/nodejs/node/pull/14781
Refs: https://tools.ietf.org/html/rfc2606#section-2


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>