[RedHat] Warn about stale ifcfg files

[priteau]

On RedHat systems, this role doesn't manage existing ifcfg files that don't match active interface names. This can cause conflicts on reboot when the OS applies all ifcfg files, including stale ones.

Could we at least warn about their presence?

[markgoddard]

It's a nice idea. There are a few challenges:

• There could be ifcfg files legitimately not managed by the role, and we don't have any way to detect which ones we generated.
• It's not easy to get a warning message to users that they will see in Ansible.