test: update net-local-address-port

- changed var to const
- changed assert.equal to assert.strictEqual

PR-URL: https://github.com/nodejs/node/pull/9885
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

test/parallel/test-net-local-address-port.js

@@ -1,11 +1,11 @@
 'use strict';
-var common = require('../common');
-var assert = require('assert');
-var net = require('net');
+const common = require('../common');
+const assert = require('assert');
+const net = require('net');
 
 var server = net.createServer(common.mustCall(function(socket) {
-  assert.equal(socket.localAddress, common.localhostIPv4);
-  assert.equal(socket.localPort, this.address().port);
+  assert.strictEqual(socket.localAddress, common.localhostIPv4);
+  assert.strictEqual(socket.localPort, this.address().port);
   socket.on('end', function() {
     server.close();
   });