Add var 'PRUNE_EXTERNAL' to arg 'all' on image prune, this arg include external image as prune candidate, for default is 'true', now we can change to 'false' to not prune external imagens.
Add var 'PRUNE_EXTERNAL' to arg 'all' on image prune, this arg include external image as prune candidate, for default is 'true', now we can change to 'false' to not prune external imagens.

getupcloud/imagepruner