[QA] enabling encryption on non-empty external storage causes errors

[jnweiger]

Seen while testing encryption 1.5.1-rc1 with hsmdaemon-0.0.8 and SoftHSM master (2.6.1+) on server 10.7.0

• Configure external storage SFTP with encryption disabled.
• Upload a files inksc.png into the SFTP storage.
• Enable encryption on the storage
• Try to move the file to the root folder, try to delete the file.
• The operations all fail. Errors appear:

Expected behaviour: should work (or enabling encryption can only be done when the storage is empty)