do not mock any ContainerBuilder methods

The tests are not expected to call any of the methods of the
`ContainerBuilder` class. Therefore, none need to be mocked. This is
needed as PHPUnit would otherwise complain about not being able to mock
the non-existent `ExpressionFunctionProviderInterface` (which is
provided by the ExpressionLanguage component, but is actually an
optional dependency here).

Author: xabbuh

Tests/Loader/LoaderFactoryTest.php

@@ -44,6 +44,7 @@ private function createMockContainerBuilder()
         return $this
             ->getMockBuilder('Symfony\Component\DependencyInjection\ContainerBuilder')
             ->disableOriginalConstructor()
+            ->setMethods(null)
             ->getMock();
     }
 }