http: remove domain specific code

Due to some changes to async tracking of http and also
in how domains are handled, it's no longer necessary
to manually copy domain from req to res in http code.

PR-URL: #18477
Refs: #16222
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

lib/_http_client.js

@@ -495,12 +495,6 @@ function parserOnIncomingClient(res, shouldKeepAlive) {
   var socket = this.socket;
   var req = socket._httpMessage;
 
-  // propagate "domain" setting...
-  if (req.domain && !res.domain) {
-    debug('setting "res.domain"');
-    res.domain = req.domain;
-  }
-
   debug('AGENT incoming response!');
 
   if (req.res) {