Use the target host and not the proxy host in the client hello request

Closes #530

library/Zend/Http/Client/Adapter/Proxy.php

@@ -244,7 +244,7 @@ class Zend_Http_Client_Adapter_Proxy extends Zend_Http_Client_Adapter_Socket
     )
     {
         $request = "CONNECT $host:$port HTTP/$http_ver\r\n" .
-                   "Host: " . $this->config['proxy_host'] . "\r\n";
+                   "Host: " . $host . "\r\n";
 
         // Process provided headers, including important ones to CONNECT request
         foreach ($headers as $k => $v) {