`/etc/bootc/config.toml` is not used by `bootc` binary

Hi there.

I'm trying to use [system-upgrade-controller](https://github.com/rancher/system-upgrade-controller/tree/master) to upgrade kubernetes cluster with bootc-based nodes. System-upgrade-controller uses privileged container and mounts hosts' `/` into the containers' `/host`, which means executing `bootc upgrade` inside this container fails (`bootc` expects `/sysroot/ostree` to be present, although in this case it is `/host/sysroot/ostree`).

To overcome this I tried to use bootc's `config.toml` as described in the https://github.com/bootc-dev/bootc/blob/main/docs/src/man/bootc-config.5.md. Although I'm still getting a message that `System is not deployed via bootc.`

Here is my `/etc/bootc/config.toml`:

```
bash-5.1# cat /etc/bootc/config.toml
[storage]
root = "/host/sysroot/ostree/"
```

Am I doing something wrong here?

Thanks!