Do not allow using deprecated options in new mode
Do not allow using deprecated options in new mode

DOCKER_ROOT_VOLUME is a deprecated option. Allow using it only in
compatibility mode.

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

Closes: #236
Approved by: rhvgoyal

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