cloud: clean up networking configuration
    
    We're no longer using legacy network scripts to bring up networking.
    We're using NetworkManager and now in F33+ networkmanager will even
    default to writing out new configuration as NM keyfiles in
    /etc/NetworkManager/system-connections/. We don't need to lay down
    a networking config for eth0. Either cloud-init will do that for us
    or NetworkManager will default to DHCP anyway.
    
    We also don't need to populate /etc/hosts as that will get done on
    boot too with the same content we were writing there already.