[BUG] Example of data migration doesn't work for hidden/./dot-files)

Used this without looking too deeply for migrating a home-assistant storage to longhorn. The db was under ".storage" which wasn't copied over:

https://github.com/longhorn/longhorn/blob/5a3f8d714bc135dfe06fee6e3f09075906dba3ea/examples/data_migration.yaml#L22

changing to

    args: [ "-c", "cp -r -v /mnt/old/. /mnt/new" ]

made my case work.