Comment 7 for bug 1907280

Prior to multi-esp curtin support I think this config would work fine even if
the additional flag: boot on the /boot partition (which is not an ESP) is
incorrect. I don't think curtin did much with a second partition flagged as
boot when in UEFI mode which is why this slipped through.

I suspect the /boot partition might trigger MAAS to auto-generate something
marking it bootable? That;s likely new in maas. Curtin has an existing
config that matches what's used in this deployment (UEFI, nvme, bcache, /boot
partition and /boot/efi) but it does not have flag:boot on the /boot
partition.

https://git.launchpad.net/curtin/tree/examples/tests/bcache-ceph-nvme.yaml