DLPX-69865 IP configuration is lost if a MAC address changes

[prakashsurya]

To make the network configuration more resilient to changes of the MAC
address, this change modifies the netplan configuration generated by
cloud-init to no longer match on the MAC address. This way, if the MAC
address of a NIC changes (which can happen in VM environments), the
network configuration on the system should still work as before.

[prakashsurya]

With this change applied:

$ cat /etc/netplan/50-cloud-init.yaml
# This file is generated from information provided by the datasource.  Changes
# to it will not persist across an instance reboot.  To disable cloud-init's
# network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
    ethernets:
        ens160:
            dhcp4: true
            match:
                name: ens160
            set-name: ens160
    version: 2

[prakashsurya]

git-ab-pre-push is here

[prakashsurya]

Also worth noting, this is only half of the solution to address DLPX-69865; I still need to develop a similar change for the configuration we generate via the DE software. I'll open a review for that once I have it ready.

[pzakha]

This LGTM.

Also, there might be another part to it, that is what to do with engines that were previously configured by cloud-init with MAC address matching. That could be addressed by your other change that tries to re-apply network configuration on each boot (although that could potentially add latency to the boot), or somehow trigger a one-time reconfiguration.