Ignition fails adding new nodes to IPI cluster after upgrading to OCP 4.12+

Issue

Adding new nodes to an OpenShift cluster that has been upgraded to 4.12+ fails with the following ignition error on the console node:

Ignition has failed. Please ensure your config is valid. Note that only
Ignition spec v3.0.0+ configs are accepted.

A CLI validation tool to check this called ignition-validate can be
downloaded from GitHub:
    https://github.com/coreos/ignition/releases

  Displaying logs from failed units: ignition-fetch-offline.service
  -- Logs begin at Thu 2020-12-10 20:52:42 UTC, end at Thu 2020-12-10 20:52:45 UTC. --
  Dec 10 20:52:44 systemd[1]: Failed to start Ignition (fetch-offline).
  Dec 10 20:52:44 ignition[836]: reading system config file "/usr/lib/ignition/user.ign"
  Dec 10 20:52:44 ignition[836]: no config at "/usr/lib/ignition/user.ign" 
  ...
  Dec 10 20:52:44 ignition[836]: failed to fetch config: unsupported config version.
  Dec 10 20:52:44 ignition[836]: failed to acquire config: unsupported config version
  Dec 10 20:52:44 ignition[836]: Ignition failed: unsupported config version