ConfigDrive: do not use 'id' on a link for the device name
'id' on a link in the openstack spec should be "Generic, generated ID". current implementation was to use the host's name for the host side nic. Which provided names like 'tap-adfasdffd'.
We do not want to name devices like that as its quite unexpected and non user friendly. So here we use the system name for any nic that is present, but then require that the nics found also be present at the time of rendering.
The end result is that if the system boots with net.ifnames=0 then it will get 'eth0' like names. and if it boots without net.ifnames then it will get enp0s1 like names.