Fix EZP-20576 - add use case when there is a custom pagelayout defined in legacy

We shouldn't use new stack pagelayout when the legacy module is asking for a custom pagelayout.

Example use-case :
- Loading ezoe in new stack : While inserting an image the eZ OE popup loads the new stack layout but it should the layout defined in legacy : popup_pagelayout.tpl


Tested manually with master