The io/ioutil package has been deprecated in Go 1.16. This commit
replaces the existing io/ioutil functions with their new definitions in
io and os packages.
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
This allows us to cache manifests and avoid extra round trips to the
registry for content we already know about.
dockerd currently does not support containerd on Windows, so this does
not store manifests on Windows, yet.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>