From the upstream launchpad https://bugs.launchpad.net/ironic/+bug/2041901

1) Create a "UEFI NVRAM Cleaning routine" in IPA.
2) Add a low numbered default clean/deploy step. The reason for cleaning is to just ensure the outdated records get removed. Consensus from the PTG was likely "just remove anything that was on a hard disk (the HD record indicator). The aspect for on-deploy as an early step is to remove before adding additional records as not to upset system firmware, and to also cover the case where a deployer runs without cleaning enabled and somehow ends up booting to the wrong OS or attempts to manually intervene at first boot of the new OS.