[rdo-list] [infra] images.rdoproject server cleanup changes

Hi, to allow rdophase2 cache servers to have the time to download the images for caching purposes, we are stopping the automatic removal of all previous promoted images at each promotion. We'll change the cleanup process to delete images after a configurable threshold in days/images numbers. This will probably impact the storage space needed, but it's essential for downstream, even more since now potentially the rhythm of promotions upstream is going to increase. Thanks.