Create an lvm-over-md layout across the two virtio scratch disks, then
test blivet's ability to populate and print the devicetree with that
setup.
Also, remove the task to copy out logs as it doesn't work.
Add missing tasks section to tests playbook.
Use an absolute path to the example script since 'dir' is always
relative to /var/str.
Must define 'dir' explicitly -- there is no default handling.
