test: var to const/let in test-tls-set-ciphers

this change is part of code and learn (NINA-2016)
PR-URL: #9877
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: rajatkumar

test/parallel/test-tls-set-ciphers.js

@@ -1,5 +1,5 @@
 'use strict';
-varcommon=require('../common');
+constcommon=require('../common');
 
 if(!common.opensslCli){
 common.skip('node compiled without OpenSSL CLI.');
@@ -11,25 +11,25 @@ if (!common.hasCrypto) {
 return;
 }
 
-varassert=require('assert');
-varexec=require('child_process').exec;
-vartls=require('tls');
-varfs=require('fs');
+constassert=require('assert');
+constexec=require('child_process').exec;
+consttls=require('tls');
+constfs=require('fs');
 
-varoptions={
+constoptions={
 key: fs.readFileSync(common.fixturesDir+'/keys/agent2-key.pem'),
 cert: fs.readFileSync(common.fixturesDir+'/keys/agent2-cert.pem'),
 ciphers: 'DES-CBC3-SHA'
 };
 
-varreply='I AM THE WALRUS';// something recognizable
-varresponse='';
+constreply='I AM THE WALRUS';// something recognizable
+letresponse='';
 
 process.on('exit',function(){
 assert.notEqual(response.indexOf(reply),-1);
 });
 
-varserver=tls.createServer(options,common.mustCall(function(conn){
+constserver=tls.createServer(options,common.mustCall(function(conn){
 conn.end(reply);
 }));