Comment 5 for bug 1449318

verified taht works with:
a.) boot wily system with no user-data at all
b.) sudo tee /etc/cloud/cloud.cfg.d/99_poweroff.cfg <<EOF
#cloud-config
runcmd:
 - "echo ------------ exiting fail ------------------; exit 1;"
power_state:
  mode: poweroff
EOF

c.) rm -Rf /var/lib/cloud
d.) sudo reboot
e.) system will come back up and not poweroff due to this bug
f.) sudo sed -i -e 's,TimeoutSec=0,TimeoutSec=0\nKillMode=process,' /lib/systemd/system/cloud-final.service
g.) sudo rm -Rf /var/lib/cloud
h.) sudo reboot

system will turn itself off after reboot.

system wil boot and poweroff