test: replaced fs.readSync with fixtures.readSync

NINA 2017 Code and Learn session for first time contributors.  This
touched test/parallel/test-https-socket-options.js to replace
common.fixturesDir

PR-URL: https://github.com/nodejs/node/pull/15882


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>