Jump to Symfony 3.4

Thanks to the BC compatibility, almost nothing have to be changed.
All changes are related to new bundle version of:
- SensioFrameworkExtraBundle
- DoctrineFixturesBundle

app/config/security.yml

@@ -31,12 +31,15 @@ security:
             fos_oauth: true
             stateless: true
             anonymous: true
+            provider: fos_userbundle
 
         login_firewall:
+            logout_on_user_change: true
             pattern: ^/login$
             anonymous:  ~
 
         secured_area:
+            logout_on_user_change: true
             pattern: ^/
             form_login:
                 provider: fos_userbundle