mkcloud: cleanup MAC calculation
mkcloud: cleanup MAC calculation

this is a followup on 7d0a3db4edd7290c3ca4613ba0f512bc855196db

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