test: use mustNotCall in test-http-eof-on-connect

Confirm that callback is not being invoked in
test-http-eof-on-connect.js.

PR-URL: https://github.com/nodejs/node/pull/13587


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>