netcardconfig: switch from `ifconfig` to `ip link` for interface parsing [Closes...

netcardconfig: switch from `ifconfig` to `ip link` for interface parsing [Closes: issue2219]

Quoting from the bug report:

| ifconfig as of Debian stretch uses a different output format.
| This breaks enumeration of devices in netcardconfig line 576.

ifconfig isn't the state-of-the-art tool anyway, so switching
to ip(8) is an excellent idea. :)

Thanks: Jakob Haufe <sur5r@sur5r.net> for the bugreport and patch