[FrameworkBundle] fixed session support in functional tests when using several clients in the same process

src/Symfony/Bundle/FrameworkBundle/Client.php

@@ -100,6 +100,7 @@ class Client extends BaseClient
         return <<<EOF
 <?php
 
+require_once '/Users/fabien/work/symfony/2_0/blog/app/bootstrap.php';
 require_once '$path';
 
 \$kernel = unserialize('$kernel');

src/Symfony/Bundle/FrameworkBundle/EventListener/TestSessionListener.php

@@ -50,6 +50,8 @@ class TestSessionListener
         $cookies = $event->getRequest()->cookies;
         if ($cookies->has(session_name())) {
             session_id($cookies->get(session_name()));
+        } else {
+            session_id('');
         }
     }