[networking] fix 'nmcli con show' usage

Fixes #377.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>
[networking] additional nmcli commands

Collect 'nmcli con show active' and 'nmcli dev show'.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>