user.* keys do not work with the nocloud datasource provided by LXD

[stew3254]

When using jinja templates for cloud-init, it's very convenient to pass custom values in by user.* and then access them by ds.config.user_*. Here is a LXD profile demonstrating an example.

name: demo
description: Jinja cloud-init demo
config:
  cloud-init.user-data: |
    ## template: jinja
    #cloud-config
    users:
      - name: "{{ ds.config.user_username }}"
        sudo: ALL=(ALL) NOPASSWD:ALL
        shell: /bin/bash
        plain_text_passwd: "{{ ds.config.user_password }}"
        lock_passwd: false
  user.password: test
  user.username: test

If you were to launch this profile on a jammy or later vm, or any container, it should create a user named test with the password test instead of the ubuntu user.

Now, add a config drive to the profile under the devices section:

devices:
  config:
    source: cloud-init:config
    type: disk

Now, the user.username and user.password variables don't get passed in via the NoCloud datasource. Therefore, the default ubuntu user is created instead. This occurs because the variables were not actually passed into the meta-data file in the root of /dev/sr0 which the drive added. Therefore, no custom variables can be passed to instances launched using this method.

Currently, this breaks tooling using Focal vms as a base image, such as those trying to reproduce Ubuntu FIPS issues because Focal does not properly implement the standard LXD datasource.