limit the impact on filesystem for rsync, as asked by infra team in https://pagure.io/fedora-infrastructure/issue/8964
note: I tested it on my computer with all languages, it takes 35 minutes instead of 2h30, which may be too good to be true :)
Pull-Request has been merged by pbokoc
limit the impact on filesystem for rsync, as asked by infra team in https://pagure.io/fedora-infrastructure/issue/8964