N°2651 rollback gitignore for lib tests dirs

Too dangerous ! We'll work properly on this but for 2.8

lib/symfony/framework-bundle/Tests/DependencyInjection/Fixtures/php/csrf.php

@@ -0,0 +1,9 @@
+<?php
+
+$container->loadFromExtension('framework', [
+    'csrf_protection' => true,
+    'form' => true,
+    'session' => [
+        'handler_id' => null,
+    ],
+]);