Merge branch '3.4' into 4.0

* 3.4:
  [HttpKernel] Better handling of legacy cache
  modify definitions only if the do exist
  [DI] Prevent a ReflectionException during cache:clear when the parent class doesn't exist
  [FrameworkBundle] Make MicroKernelTraitTest green
  don't override existing verbosity env var
  [HttpKernel] Read $_ENV when checking SHELL_VERBOSITY
  Remove unreachable code
  Automatically enable the CSRF protection if CSRF manager exists
  bumped Symfony version to 3.4.0
  adding checks for the expression language
  updated VERSION for 3.4.0-RC2
  updated CHANGELOG for 3.4.0-RC2

Author: xabbuh

DependencyInjection/Configuration.php

@@ -21,6 +21,7 @@
 use Symfony\Component\Form\Form;
 use Symfony\Component\Lock\Lock;
 use Symfony\Component\Lock\Store\SemaphoreStore;
+use Symfony\Component\Security\Csrf\CsrfTokenManagerInterface;
 use Symfony\Component\Serializer\Serializer;
 use Symfony\Component\Translation\Translator;
 use Symfony\Component\Validator\Validation;
@@ -109,7 +110,7 @@ private function addCsrfSection(ArrayNodeDefinition $rootNode)
         $rootNode
             ->children()
                 ->arrayNode('csrf_protection')
-                    ->canBeEnabled()
+                    ->{!class_exists(FullStack::class) && class_exists(CsrfTokenManagerInterface::class) ? 'canBeDisabled' : 'canBeEnabled'}()
                 ->end()
             ->end()
         ;

Tests/Kernel/MicroKernelTraitTest.php

@@ -18,7 +18,7 @@ class MicroKernelTraitTest extends TestCase
 {
     public function test()
     {
-        $kernel = new ConcreteMicroKernel('test', true);
+        $kernel = new ConcreteMicroKernel('test', false);
         $kernel->boot();
 
         $request = Request::create('/');
@@ -31,7 +31,7 @@ public function test()
 
     public function testAsEventSubscriber()
     {
-        $kernel = new ConcreteMicroKernel('test', true);
+        $kernel = new ConcreteMicroKernel('test', false);
         $kernel->boot();
 
         $request = Request::create('/danger');