Fix conflict between UrlGeneratorInterface(s) (#4663)

They’re was a problem with the name of the interface UrlGeneratorInterface, used twice in AbstractAdmin
PHP Fatal error:  Cannot use Symfony\\Component\\Routing\\Generator\\UrlGeneratorInterface as UrlGeneratorInterface because the name is already in use in […]/app/cache/dev/classes.php on line 12223

Admin/AbstractAdmin.php

@@ -40,7 +40,7 @@ use Symfony\Component\Form\Form;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\PropertyAccess\PropertyPath;
-use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
+use Symfony\Component\Routing\Generator\UrlGeneratorInterface as RoutingUrlGeneratorInterface;
 use Symfony\Component\Security\Acl\Model\DomainObjectInterface;
 use Symfony\Component\Security\Core\Exception\AccessDeniedException;
 use Symfony\Component\Translation\TranslatorInterface;
@@ -1191,7 +1191,7 @@ abstract class AbstractAdmin implements AdminInterface, DomainObjectInterface
     /**
      * {@inheritdoc}
      */
-    public function generateObjectUrl($name, $object, array $parameters = array(), $absolute = UrlGeneratorInterface::ABSOLUTE_PATH)
+    public function generateObjectUrl($name, $object, array $parameters = array(), $absolute = RoutingUrlGeneratorInterface::ABSOLUTE_PATH)
     {
         $parameters['id'] = $this->getUrlsafeIdentifier($object);
 
@@ -1201,7 +1201,7 @@ abstract class AbstractAdmin implements AdminInterface, DomainObjectInterface
     /**
      * {@inheritdoc}
      */
-    public function generateUrl($name, array $parameters = array(), $absolute = UrlGeneratorInterface::ABSOLUTE_PATH)
+    public function generateUrl($name, array $parameters = array(), $absolute = RoutingUrlGeneratorInterface::ABSOLUTE_PATH)
     {
         return $this->routeGenerator->generateUrl($this, $name, $parameters, $absolute);
     }
@@ -1209,7 +1209,7 @@ abstract class AbstractAdmin implements AdminInterface, DomainObjectInterface
     /**
      * {@inheritdoc}
      */
-    public function generateMenuUrl($name, array $parameters = array(), $absolute = UrlGeneratorInterface::ABSOLUTE_PATH)
+    public function generateMenuUrl($name, array $parameters = array(), $absolute = RoutingUrlGeneratorInterface::ABSOLUTE_PATH)
     {
         return $this->routeGenerator->generateMenuUrl($this, $name, $parameters, $absolute);
     }