freshvm: Use qcow2 img to improve startup time
freshvm: Use qcow2 img to improve startup time

Instead of copying and converting from qcow2 to raw, just
use a backing file with qcow.
Also remove some dead code.

gosipyan/automation,gosipyan/automation,SUSE-Cloud/automation,vmoravec/automation,aspiers/automation,aspiers/automation,aspiers/automation,SUSE-Cloud/automation,SUSE-Cloud/automation,gosipyan/automation,SUSE-Cloud/automation,vmoravec/automation,gosipyan/automation,vmoravec/automation,vmoravec/automation,aspiers/automation