change to local function instead of prototype

Author: evantorrie

lib/_http_agent.js

@@ -206,13 +206,13 @@ Agent.prototype.createSocket = function createSocket(req, options, cb) {
     }
     self.sockets[name].push(s);
     debug('sockets', name, self.sockets[name].length);
-    self._installListeners(s,options);
+    installListeners(self, s, options);
     cb(null, s);
   }
 };
 
-Agent.prototype._installListeners = function installListeners(s, options) {
-  var self = this;
+function installListeners(agent, s, options) {
+  var self = agent;
 
   function onFree() {
     debug('CLIENT socket onFree');