test: minor refactoring of onticketkeycallback

The motivation for this commit is to make the the onticketkeycallback
function more readable.

PR-URL: https://github.com/nodejs/node/pull/24718


Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>