storage-setup: Use a variable for default percent size of a volume group
storage-setup: Use a variable for default percent size of a volume group

Use a variable DEFAULT_DATA_SIZE_PERCENT, to figure out default percentage
which needs to be used while createing a data LV. No functionality change.
 
Signed-off-by: Vivek Goyal <61d11262d0d9873ddb5a887f48fcb04e8c5973d0@redhat.com>

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