we now, by default, only prune dangling images. if --all is passed, we
prune dangling images AND images that do not have an associated containers.
also went ahead and enabled the podman-remote image prune side of things.
Fixes: #2192
Signed-off-by: baude <bbaude@redhat.com>
Allow user to prune unused/unnamed images, the layer images from building,
via podman rmi --prune.
Allow user to prune stopped/exiuted containers via podman rm --prune.
This should resolve#1910
Signed-off-by: baude <bbaude@redhat.com>