Add test for setup and tear down of overlay2 graph driver
Add test for setup and tear down of overlay2 graph driver

Along the lines of overlay, add test for overlay2.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

Closes: #154
Approved by: cgwalters

thescriptbender/container-storage-setup,shishir-a412ed/docker-storage-setup