Detect when parted changes PARTUUID

[Drewsif]

Parted sometimes changes the partuuid, or at least it used to. It would be nice to detect the change and update the image so that it can boot.

See also:

• https://raspberrypi.stackexchange.com/questions/68082/why-wont-my-raspberrypi-boot-if-i-use-parted-to-adjust-the-partition

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