Revert "views: Update dt_view_get_image_to_act_on for zoom==1 & full_preview."

This reverts commit ebcc7c27edb72c190b3392e254395c9d452f877c.

This commit changed the size of the settings struct stored in db so we
drop it when loading an old db.
TODO:
- fix this commit (lemagoup is already working on it)
- stop writing this stuff to db