When given the "run" argument, in addition to launching `podman system
service` in the background, also start a small periodic maintenance
script. It's only job is to clean up stale images, containers, and
volumes from old jobs. Currently hard-coded to trigger every 2 days,
this could be tweaked via build-args or env. var.
Signed-off-by: Chris Evich <cevich@redhat.com>
