Move TestOpenRead to `-test.root`
Move TestOpenRead to `-test.root`

This test requires root for FUSE-related operation. We should move it to
`-test.root` for make "make test" succeed for non-root users.

Signed-off-by: Kohei Tokunaga <72a466a7d91579e23b8af87d6766ee221241ce87@gmail.com>

containerd/stargz-snapshotter,containerd/stargz-snapshotter,containerd/stargz-snapshotter,containerd/stargz-snapshotter