meta-lxatac-software: rauc bundle: hook.sh fix lxa-iobus cache migration

[hnez]

The lxa-iobus server maintains a cache of IOBus node IDs it has seen before to speed up re-discovery of said nodes (known IDs are tried before performing a full LSS scan).

This cache is stored in /var/cache/lxa-iobus/lss-cache.

The migrate function in hook.sh only works on files, so it will not currently migrate the lss-cache inside of /var/cache/lxa-iobus. Fix that by pointing to the file directly. Also make sure the directory to migrate to exists on the system.

TODO:

• [x] I can not be trusted to write two correct lines of bash at a time. Make sure this actually does what it is supposed to by testing.

[SmithChart]

Tested and migrated my lss-cache as expected. (Also the /etc/labgrid/userconfig.yaml was migrated as expected.)