Restore procedure error with stale destination contents

[nrauso]

The restore procedure for a backed-up module fails if a config file exists in the root path of the backup repository.
When this happens, the restore attempt results in the following error:

Traceback (most recent call last):
  File "/var/lib/nethserver/cluster/actions/read-backup-repositories/50read", line 56, in <module>
    restic_prefix, restic_uuid, _ = oroot["Path"].split("/", 2)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: not enough values to unpack (expected 3, got 1)

This typically occurs if the repository was previously used for an NS7 backup with restic.
In such cases, the repository content might look like this:

#$ rclone-wrapper 1 lsf REMOTE_PATH
config
data/
dump.json.gz.gpg
index/
keys/
ldapproxy/
loki/
snapshots/
traefik/

Could be a good idea try to prevent this behavior.

[DavidePrincipi]

In Testing Core 3.9.0-dev.2

Test case

Check the bug is not reproducible with the Testing version.

To manually reproduce the stale contents,

1. Backup Traefik instance to a local repository on the node itself.

2. Generate a bogus "config" file:

   runagent -m traefik1 rclone-wrapper 1 touch REMOTE_PATH/config 
   

[nrauso]

test case: VERIFIED