VAAPI: Take more care when probing filters

- Don't try to access the image pitches when vaDeriveImage produce an error
- Don't try to delete an image_id that was not setup properly before
- Only continue checking when no check was false yet

This fixes a segfault on machines that don't support vaDeriveImage, like our fglrx friends :-)
drop check for status. assume a future change adds some api call after vaDeriveImage which fails. this code would not destroy the image then (it is not derive_image_status). testing for image.image_id != VA_INVALID_ID should be enough.