Use === instead of == for END_OF_FILE compares

This caused a very hard to track down bug. Thanks to Mikeal Rogers for this
fix. Unfortunately we were unable to put together a test case.

lib/net.js

@@ -382,7 +382,7 @@ Object.defineProperty(Stream.prototype, 'readyState', {
 Stream.prototype.write = function (data, encoding) {
   if (this._writeQueue && this._writeQueue.length) {
     // Slow. There is already a write queue, so let's append to it.
-    if (this._writeQueueLast() == END_OF_FILE) {
+    if (this._writeQueueLast() === END_OF_FILE) {
       throw new Error('Stream.close() called already; cannot write.');
     }
     this._writeQueue.push(data); // TODO if string of the same encoding concat?
@@ -511,7 +511,7 @@ Stream.prototype.flush = function () {
     var data = this._writeQueue.shift();
     var encoding = this._writeQueueEncoding.shift();
 
-    if (data == END_OF_FILE) {
+    if (data === END_OF_FILE) {
       this._shutdown();
       return true;
     }
@@ -714,7 +714,7 @@ Stream.prototype.close = function (data, encoding) {
 Stream.prototype.end = function (data, encoding) {
   if (this.writable) {
     if (data) this.write(data, encoding);
-    if (this._writeQueueLast() != END_OF_FILE) {
+    if (this._writeQueueLast() !== END_OF_FILE) {
       this._writeQueue.push(END_OF_FILE);
       this.flush();
     }