* dev-setup.c: when running in a container, create a tiny stub udev
database with the systemd tag set for all network interfaces found,
so that libudev reports them as present, and systemd's .device units
* dev-setup.c: when running in a container, create a tiny stub udev
database with the systemd tag set for all network interfaces found,
so that libudev reports them as present, and systemd's .device units