This create more issues than it solves:
* override existing subuid / subgid
* not flexible for the end user
* it has to be created only once (while tmpfiles always try to create
those files)
I think Flatcar should not be responsible to create this and it should
be documented on how to do it through Ignition:
```yaml
version: 1.1.0
variant: flatcar
storage:
files:
- path: /etc/subuid
append:
- inline: |
root:1065536:65536
- path: /etc/subgid
append:
- inline: |
root:1065536:65536
```
Signed-off-by: Mathieu Tortuyaux <mtortuyaux@microsoft.com>
fcb6e97776