Do not rely on ifcfg-eth0 existing in the guest image
Do not rely on ifcfg-eth0 existing in the guest image

We currently just do a cp /etc/sysconfig/network-scripts/ifcfg-eth0 to
all the nics we need to generate. The assumption that ifcfg-eth0 always
exists has been broken with the last rhel8.4 images, so let's just
inject the content of ifcfg-eth0 and make this whole thing more
declarative.

Tested this on both OSP13 and OSP16.

Change-Id: I57924e469d0cc5295fb280b521e0ca001a037c8b

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared