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/Functional/app/ContainerDebug/config.yml

@@ -0,0 +1,10 @@
+imports:
+    - { resource: ../config/default.yml }
+
+services:
+    _defaults: { public: true }
+    public:
+        class: Symfony\Bundle\FrameworkBundle\Tests\Fixtures\DeclaredClass
+    private_alias:
+        alias: public
+        public: false