[FrameworkBundle] Subrequests should always use GET method

src/Symfony/Bundle/FrameworkBundle/HttpKernel.php

@@ -140,6 +140,7 @@ class HttpKernel extends BaseHttpKernel
 
             $options['attributes']['_route'] = '_internal';
             $subRequest = $request->duplicate($options['query'], null, $options['attributes']);
+            $subRequest->setMethod('GET');
         }
 
         $level = ob_get_level();