fixed video thumbnail uploads to backblaze

[ggg7125]

when nodetube auto-generated video thumbnails it creates them as jpg, but then tries to locate and upload it to backblaze as a png, resulting in a "file not found" error. so i simply changed it to locate a jpg and now it all works

[BassOfBass]

@mayeaux is there a particular reason to check for "production" env for backblaze? How are people supposed to test it in dev mode?