Adaptations for CVE-2025-9615

[danfruehauf]

See also:
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/2325

Any file access within the plugin should take implement safe access. At the moment this boils down to:

• Key authentication access (accessing the private key)
• Known hosts file

Up until then, with the deployed NetworkManager version, only "admin" users (belonging to wheel, or equivalent) will be able to operate those connections.

[danfruehauf]

Addressed by #137