Fix a test which wasn't explicitly setting THUMBNAIL_DEBUG like it should have been
Fix a test which wasn't explicitly setting THUMBNAIL_DEBUG like it should have been

jrief/easy-thumbnails,SmileyChris/easy-thumbnails,sandow-digital/easy-thumbnails-cropman,siovene/easy-thumbnails,Mactory/easy-thumbnails,sandow-digital/easy-thumbnails-cropman,jrief/easy-thumbnails,emschorsch/easy-thumbnails,emschorsch/easy-thumbnails,jaddison/easy-thumbnails