Bad owner or permissions on /home/user/.config/cmlxc/ssh-config

I'm running a setup without incus-admin, I'm only in the incus group. Everything works fine, except:

```
$ ssh cm0
Bad owner or permissions on /home/user/.config/cmlxc/ssh-config
$ ls -la /home/user/.config/cmlxc/ssh-config
-rw-rw-r-- 1 user incus 842 Sep 1 11:54 /home/user/.config/cmlxc/ssh-config
```

Luckily, this fix works:

```
$ chown user: /home/user/.config/cmlxc/ssh-config
$ ssh cm0
Linux cm0-localchat 6.14.0-37-generic #37~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Thu Nov 20 10:25:38 UTC 2 x86_64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
root@cm0-localchat:~#
```

Start by reproducing the setup with only membership in the incus group and inspect how /home/user/.config/cmlxc/ssh-config is created or updated. Done means the file has ownership and permissions accepted by ssh without manually running chown, and ssh cm0 connects successfully.

Written by the indexing model from the issue text.