net: simplify net.Socket#end()

`writable` is already set by the streams side, and
there is a handler waiting for the writable side to finish
which already takes care of the other cleanup code that
was previously there; both of these things can therefore be removed.

PR-URL: #18708
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

lib/net.js

@@ -496,18 +496,10 @@ Socket.prototype._read = function(n) {
 };
 
 
-Socket.prototype.end = function(data, encoding) {
-  stream.Duplex.prototype.end.call(this, data, encoding);
-  this.writable = false;
+Socket.prototype.end = function(data, encoding, callback) {
+  stream.Duplex.prototype.end.call(this, data, encoding, callback);
   DTRACE_NET_STREAM_END(this);
   LTTNG_NET_STREAM_END(this);
-
-  // just in case we're waiting for an EOF.
-  if (this.readable && !this._readableState.endEmitted)
-    this.read(0);
-  else
-    maybeDestroy(this);
-
   return this;
 };