storage-setup: Use variables for some often used strings
storage-setup: Use variables for some often used strings

Instead of hardcoding "docker-data" and "docker=meta" everywhere, use
bash variables.

No functionality change.

Signed-off-by: Vivek Goyal <61d11262d0d9873ddb5a887f48fcb04e8c5973d0@redhat.com>

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