Fix issues loading response classes from plugins.

Fixes #2759

lib/Cake/Network/Http/HttpSocket.php

@@ -390,11 +390,10 @@ class HttpSocket extends CakeSocket {
 		}
 
 		list($plugin, $responseClass) = pluginSplit($this->responseClass, true);
-		App::uses($this->responseClass, $plugin . 'Network/Http');
+		App::uses($responseClass, $plugin . 'Network/Http');
 		if (!class_exists($responseClass)) {
 			throw new SocketException(__d('cake_dev', 'Class %s not found.', $this->responseClass));
 		}
-		$responseClass = $this->responseClass;
 		$this->response = new $responseClass($response);
 		if (!empty($this->response->cookies)) {
 			if (!isset($this->config['request']['cookies'][$Host])) {