test: improve code in test-http-bind-twice.js

* use const instead of var for required modules
* use assert.strictEqual instead of assert.equal
PR-URL: #10318
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Italo A. Casas <me@italoacasas.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: edsadr

test/parallel/test-http-bind-twice.js

@@ -1,15 +1,15 @@
 'use strict';
 constcommon=require('../common');
-varassert=require('assert');
-varhttp=require('http');
+constassert=require('assert');
+consthttp=require('http');
 
-varserver1=http.createServer(common.fail);
+constserver1=http.createServer(common.fail);
 server1.listen(0,'127.0.0.1',common.mustCall(function(){
-varserver2=http.createServer(common.fail);
+constserver2=http.createServer(common.fail);
 server2.listen(this.address().port,'127.0.0.1',common.fail);
 
 server2.on('error',common.mustCall(function(e){
-assert.equal(e.code,'EADDRINUSE');
+assert.strictEqual(e.code,'EADDRINUSE');
 server1.close();
 }));
 }));