test: use common/fixtures module instead of common.fixturesDir in test/parallel/test-https-localaddress.js

Author: CharlesWall

test/parallel/test-https-localaddress.js

@@ -27,13 +27,13 @@ if (!common.hasCrypto)
 if (!common.hasMultiLocalhost())
   common.skip('platform-specific test.');
 
-const fs = require('fs');
+const fixtures = require('../common/fixtures');
 const assert = require('assert');
 const https = require('https');
 
 const options = {
-  key: fs.readFileSync(`${common.fixturesDir}/keys/agent1-key.pem`),
-  cert: fs.readFileSync(`${common.fixturesDir}/keys/agent1-cert.pem`)
+  key: fixtures.readKey('agent1-key.pem'),
+  cert: fixtures.readKey('agent1-cert.pem')
 };
 
 const server = https.createServer(options, function(req, res) {