test: remove unused variables from net tests

Remove a handful of variables that are declared but never used in the
tests for the net module.

PR-URL: #4430
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-net-create-connection.js

@@ -22,7 +22,7 @@ server.listen(tcpPort, 'localhost', function() {
 
   function fail(opts, errtype, msg) {
     assert.throws(function() {
-      var client = net.createConnection(opts, cb);
+      net.createConnection(opts, cb);
     }, function(err) {
       return err instanceof errtype && msg === err.message;
     });

test/parallel/test-net-dns-custom-lookup.js

@@ -2,7 +2,6 @@
 var common = require('../common');
 var assert = require('assert');
 var net = require('net');
-var dns = require('dns');
 var ok = false;
 
 function check(addressType, cb) {

test/parallel/test-net-dns-lookup-skip.js

@@ -1,6 +1,5 @@
 'use strict';
 var common = require('../common');
-var assert = require('assert');
 var net = require('net');
 
 function check(addressType) {

test/parallel/test-net-listen-close-server.js

@@ -2,7 +2,6 @@
 var common = require('../common');
 var assert = require('assert');
 var net = require('net');
-var gotError = false;
 
 var server = net.createServer(function(socket) {
 });

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

@@ -3,7 +3,7 @@ var common = require('../common');
 var assert = require('assert');
 var net = require('net');
 
-var conns = 0, conns_closed = 0;
+var conns = 0;
 
 var server = net.createServer(function(socket) {
   conns++;

test/parallel/test-net-localerror.js

@@ -17,6 +17,6 @@ connect({
 
 function connect(opts, msg) {
   assert.throws(function() {
-    var client = net.connect(opts);
+    net.connect(opts);
   }, msg);
 }

test/parallel/test-net-reconnect.js

@@ -5,7 +5,6 @@ var assert = require('assert');
 var net = require('net');
 
 var N = 50;
-var c = 0;
 var client_recv_count = 0;
 var client_end_count = 0;
 var disconnect_count = 0;