Avoid VolSync permission errors when restoring PVC from backup

[martinohmann]

ext4-based volumes (like the ones created via the longhorn storage class) automatically create a lost+found directory owned by root, which causes permission errors if the volsync mover runs rootless.

Some potential options to fix this:

• Run the movers as root and use a securityContext in the app pods which employs fsGroupChangePolicy to fix the permissions
• Use longhorn-xfs storage class which does not create lost+found. In my last test this caused problems with RWX volumes though.
• Instruct restic in the movers to ignore lost+found both during backup and restore.