Clean up cached machine images

When initing machines, we download a machine image, and uncompress and
copy the image for the actual vm image. When a user constantly pulls new
machines, there may be a buildup of old, unused machine images. This
commit cleans ups the unused cached images.

Changes:
- If the machine is pulled from a URL or from the FCOS releases, we pull
  them into XDG_DATA_HOME/containers/podman/machine/vmType/cache
- Cache cleanups only happen if there is a cache miss, and we need to
  pull a new image
- For Fedora and FCOS, we actually use the cache, so we go through the
  cache dir and remove any images older than 2 weeks (FCOS's release cycle), on a cache miss.
- For generic files pulled from a URL, we don't actually cache, so we
  delete the pulled file immediately after creating a machine image
- For generic files from a local path, the original file will never be
  cleaned up

Note that because we cache in a different dir, this will not clean up
old images pulled before this commit.

[NO NEW TESTS NEEDED]

Signed-off-by: Ashley Cui <acui@redhat.com>

0 files changed, 0 insertions, 0 deletions