[RFE] Move to nmcli or nmstate to replace shell hacking

[e-minguez]

Describe the bug
Currently there are ifcfg-* files all around and it seems they are deprecated in RHEL8. Instead we should move to a more declarative way of doing it (like using nmstate) or at least NetworkManager stuff

To Reproduce
Try to setup the network in the RHEL8 way.

Expected/observed behavior
Currently ifcfg-* files are used and the legacy network service.

Additional context
Related to #688 and #689

[celebdor]

can you provide some example of those ifcfg files?

[e-minguez]

can you provide some example of those ifcfg files?

As in #688 comments, network scripts has been deprecated in RHEL8 so if you don't enable the deprecated network service and reboot the helper node, the ifcfg-baremetal and ifcfg-provisioning files are not processed, hence not reachable.

[hardys]

can you provide some example of those ifcfg files?

They're here:

https://github.com/openshift-metal3/dev-scripts/blob/master/02_configure_host.sh#L83..L109

The issue is that we should probably stop inlining the now-deprecated ifcfg files, and instead either use nmcli in those scripts, or perhaps nmstate to configure things declaratively.