When using specific view_default_layout for different siteaccesses, admin preview will always use the default one (either the default configured from DemoBundle if left in parameters.yml, or EzPublishLegacyBundle::legacy_view_default_pagelayout.html.twig), even when changing the preview SiteAccess.

Steps to reproduce with DemoBundle:
1. Define a view_default_layout for a siteaccess (e.g. ezpublish_legacy.ezdemo_site.view_default_layout: "eZDemoBundle::pagelayout.html.twig"
2. Ensure you remove ezpublish_legacy.default.view_default_layout from parameters.yml
3. Go to admin and edit a content that is not rendered directly by Symfony (e.g. /Shopping/Products/eZ-Publish-Community-Mug)
4. Click on preview, your content will not be displayed with wanted layout.