Make jp_carousel_load_for_images_linked_to_file filter works when Photon is activated

[stoyan0v]

Fixes #6054

If we have add_filter( 'jp_carousel_load_for_images_linked_to_file', '__return_true' ); and Photon activated, single image carousel doesn't work.

There is a check, that fails because Photon adds ?fit= parameter to image URL in data-orig-file attribute.
A variable that contains the URL, with omitted attributes, used in the if statement fix the problem.

Testing instructions:

• Set add_filter( 'jp_carousel_load_for_images_linked_to_file', '__return_true' );
• Activate Photon and Carousel
• Create a post with an image that is linked to its' full size file
• Click on the image on the frontend
• It should be open in lightbox

[rcoll]

This was already fixed in #6296 - will send props to Stoyan0v also :-)