test: cleanup test-child-process-disconnect.js

Changed var --> const and let
Changed assert.equal --> assert.strictEqual

PR-URL: https://github.com/nodejs/node/pull/8602
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>

test/parallel/test-child-process-disconnect.js

@@ -1,14 +1,14 @@
 'use strict';
 const common = require('../common');
-var assert = require('assert');
-var fork = require('child_process').fork;
-var net = require('net');
+const assert = require('assert');
+const fork = require('child_process').fork;
+const net = require('net');
 
 // child
 if (process.argv[2] === 'child') {
 
   // Check that the 'disconnect' event is deferred to the next event loop tick.
-  var disconnect = process.disconnect;
+  const disconnect = process.disconnect;
   process.disconnect = function() {
     disconnect.apply(this, arguments);
     // If the event is emitted synchronously, we're too late by now.
@@ -17,7 +17,7 @@ if (process.argv[2] === 'child') {
     function disconnectIsNotAsync() {}
   };
 
-  var server = net.createServer();
+  const server = net.createServer();
 
   server.on('connection', function(socket) {
 
@@ -45,10 +45,10 @@ if (process.argv[2] === 'child') {
 
 } else {
   // testcase
-  var child = fork(process.argv[1], ['child']);
+  const child = fork(process.argv[1], ['child']);
 
-  var childFlag = false;
-  var parentFlag = false;
+  let childFlag = false;
+  let parentFlag = false;
 
   // when calling .disconnect the event should emit
   // and the disconnected flag should be true.
@@ -64,7 +64,7 @@ if (process.argv[2] === 'child') {
     if (obj && obj.msg === 'ready') {
 
       // connect to child using TCP to know if disconnect was emitted
-      var socket = net.connect(obj.port);
+      const socket = net.connect(obj.port);
 
       socket.on('data', function(data) {
         data = data.toString();
@@ -84,7 +84,7 @@ if (process.argv[2] === 'child') {
   });
 
   process.on('exit', function() {
-    assert.equal(childFlag, false);
-    assert.equal(parentFlag, false);
+    assert.strictEqual(childFlag, false);
+    assert.strictEqual(parentFlag, false);
   });
 }