policy: unblock the autoconnect for children when parent is available

Summary

(Describe what the merge request does)

Purpose

(Describe why the merge request is useful, which use cases it addresses, which issue it fixes)

Checklist

Please read https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/main/CONTRIBUTING.md before opening the merge request. In particular, check that:

• the subject for all commits is concise and explicative
• the message for all commits explains the reason for the change
• the source is properly formatted
• any relevant documentation is up to date
• you have added unit tests if applicable
• the NEWS file is updated when the change deserves to be mentioned, for example for new features, behavior changes, API deprecations, etc.

Test: NetworkManager-ci!1735 (merged)