test: Updating vars to const and tsl server test

PR-URL: nodejs#9874
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-tls-timeout-server.js

@@ -1,28 +1,28 @@
 'use strict';
-var common = require('../common');
+const common = require('../common');
 
 if (!common.hasCrypto) {
   common.skip('missing crypto');
   return;
 }
-var tls = require('tls');
+const tls = require('tls');
 
-var net = require('net');
-var fs = require('fs');
+const net = require('net');
+const fs = require('fs');
 
-var options = {
+const options = {
   key: fs.readFileSync(common.fixturesDir + '/keys/agent1-key.pem'),
   cert: fs.readFileSync(common.fixturesDir + '/keys/agent1-cert.pem'),
   handshakeTimeout: 50
 };
 
-var server = tls.createServer(options, common.fail);
+const server = tls.createServer(options, common.fail);
 
 server.on('tlsClientError', common.mustCall(function(err, conn) {
   conn.destroy();
   server.close();
 }));
 
-server.listen(0, function() {
+server.listen(0, common.mustCall(function() {
   net.connect({ host: '127.0.0.1', port: this.address().port });
-});
+}));