Enhanced configuration of LV path specification
BACKUP_LVS's format needs changing.
Instead of just the LV, we need...
VG/LV,bindmount[,bindmount]...
This allows the host bind mount specification in the following...
lvm-raid/root,/boot
instead of having a separate backupstep code block with....
--lvm-snapshot lvm-raid/root \
--bind-mount /boot:/boot \
Bind mounts must be split off with -d, -f2- , put into an array, and output as
--bindmount "$ITEM:$ITEM"