Comment 3 for bug 1640635

Trying another time. Again, clean instance. This time using a very minimal cloud.cfg:

$ cat /etc/cloud/cloud.cfg
users:
   - default

datasource_list: ['OpenStack']
datasource:
   OpenStack:
     metadata_urls: ['http://169.254.169.254']
     timeout: 10
     max_wait: 20

cloud_init_modules:
 - users-groups

system_info:
   distro: ubuntu
   default_user:
    name: opc
    lock_passwd: true
    gecos: Oracle Public Cloud User
    groups: [wheel, adm, audio, cdrom, dialout, dip, floppy, lxd, netdev, plugdev, sudo, video]
    sudo: ["ALL=(ALL) NOPASSWD:ALL"]
    shell: /bin/bash
   paths:
      cloud_dir: /var/lib/cloud/
      templates_dir: /etc/cloud/templates/
      upstart_dir: /etc/init/
   ssh_svcname: ssh

$ echo "network: {config: disabled}" | sudo tee /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg
network: {config: disabled}
$ sudo rm /etc/network/interfaces/50-cloud-init.cfg
rm: cannot remove '/etc/network/interfaces/50-cloud-init.cfg': Not a directory

And again after a reboot:

$ cat /etc/network/interfaces.d/50-cloud-init.cfg
# This file is generated from information provided by
# the datasource. Changes to it will not persist across an instance.
# To disable cloud-init's network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
auto lo
iface lo inet loopback

# control-manual ens2f0
iface ens2f0 inet dhcp
    broadcast 10.0.0.255
    dns-nameservers 169.254.169.254
    gateway 10.0.0.1
    netmask 255.255.255.0

$ grep "INFO.*disabled" /var/log/cloud-init.log
$

I've attached a cloud-init log from this run as well. Hopefully should be more succinct.