Upgrade Reliability

[milas]

I've done successful upgrades now from the same version to itself on test nodes and then eventually on my "production" nodes from v1.3.0 (my own test builds) to v1.3.1-rock5b from the CI pipeline.

Need to use --preserve

When I did NOT use --preserve once, I got this error:

Error: error restoring contents for "BOOT":
    error creating directory "/system/mnt/lost+found" mode drwx------:
           mkdir /system/mnt/lost+found: file exists

(formatted for legibility above, no line breaks in the logs)

[milas]

Fixed in v1.3.2-rock5b by fddf5a9:

As this fork uses ext4 for the BOOT partition for compatibility
with the vendor U-Boot, /lost+found exists on that (unlike the
xfs partitions, which do not).

As a result, the archiver needs to be ignored when preserving the
filesystem or the installer will fail at upgrade to to the directory
already existing on the new partition.

For safety/sanity, any files in /lost+found are also ignored.
Given that /boot is read-only, there isn't really anything we
should ever need to manually restore from this partition.

This is intended to fix upgrades without --preserve.