Fix turning off VPN
If a device has multiple connections set up, then at most one of those can be active at a time, which is why they are presented as radio items.
In contrast, VPN connections are not mutually exclusive, each can be turned on or off independently. Setting :radio-mode on them currently means that VPN connections can be activated, but never disabled.
So instead of abusing the :radio-mode property to give VPN items the UI we want, use regular items that reflect the desired behavior and explicitly set up the UI the way we want.
Fixes #5779 (closed)
Edited by Florian Müllner