tardev: use containerd's local store to fetch images

So tardev-snapshotter is not a "remote" snapshotter anymore (so we can't
do lazy-pulling) but this allows containerd to be the one downloading
images, which means the snapshotter doesn't have to get credentials
before it can use authenticated registries.

Signed-off-by: Wedson Almeida Filho <[email protected]>

Author: wedsonaf