fix: Use OCP\IAppConfig instead of OCP\IConfig to prevent config error

[R0Wi]

When using the CLI to register a daemon

php occ app_api:daemon:register --set-default --harp --harp_frp_address "appapi-harp:8782" --harp_shared_key "<pass>" "harp_proxy_docker" "HaRP Proxy (Docker)" "docker-install" "http" "appapi-harp:8780" "http://my-nc-instance.com"

I'm getting:

In AppConfig.php line 873:
                                                           
  conflict between new type (mixed) and old type (string)

I think the problem only occurs when I already had a previous daemon installed which I uninstalled first.

This PR does not only resolve the problem but also removes the use of a deprecated NC function.

[kyteinsky]

thanks!
It seems this one instance was not converted to IAppConfig which resulted in the conflict.

[oleksandr-nc]

We need a fix for this fix. default_daemon_config treated everywhere as lazy setting.

Will open a PR for this.

[oleksandr-nc]

/backport to stable32

[oleksandr-nc]

It's better to do it with two backports so as not to lose the git history

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