Allow to make network configuration mandatory

[champtar]

I'm building an appliance ISO installing an rpm-ostree system.
This appliance doesn't make sense without network but there is no clean/easy way to make the Network menu mandatory.

For now I'm patching usr/lib64/python3.6/site-packages/pyanaconda/ui/{tui,gui}/spokes/network.py
and put that into product.img, but I would love if there was a boolean in the anaconda product conf file.

[poncovka]

Could you post here your patch to get a better idea of the feature, please?