general: test new features of nm-ifup scripts
From now on, ifup/ifdown scripts should be able to:
- bring up/down connection defined elsewhere than in ifcfg scripts
- load new connection at "ifup NAME" from "ifcfg-NAME" file
commit: NetworkManager@30e74005 bug: https://bugzilla.redhat.com/show_bug.cgi?id=1954607#c5