test: use strictEqual() domain-http

did this at nina 2016 na code and learn event

PR-URL: https://github.com/nodejs/node/pull/9996


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>