Missing DNS resolution causes build timeout for atb-attacker-image

Disabling systemd-resolved via the disableresolved role for the atb-attacker-image causes build errors while creating the atb-attacker-image:

` openstack.builder: fatal: [default]: FAILED! => {"msg": "Timeout (12s) waiting for privilege escalation prompt: "}`

It takes more than 12s since `sudo -i` tries to resolve the hostname (tested on the machine spawned by packer).