http,https: avoid instanceof for WHATWG URL

PR-URL: https://github.com/nodejs/node/pull/12983


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>