Rename SQL dump output file to backup.sql

[stephdl]

Rename the SQL dump output file from timescale.sql to backup.sql to fix the restoration issue

NethServer/dev#7203

• what it works: restore on the same node
  do a backup of the controller with an attached nethsecurity instance
  restore the backup on the same node and replace the ns8-nethsecurity-controller instance
  the restoration goes well
  the NethSecurity instance is not seen online from the controller
  inside the NethSecurity, we see the controller online
  restart the Nethsecurity connection inside the controller menu of NethSecurity and the instance is seen online inside the controller

The restart of NethSecurity seems a mandatory

• what it does not work without manual interaction: restore on another node
  do a backup of the controller with an attached nethsecurity instance
  restore the backup on another node and replace the ns8-nethsecurity-controller instance
  the restoration goes well
  the NethSecurity instance is not seen online from the controller
  inside the NethSecurity, we do not see the controller online
  set a new FQDN to the controller because the FQDN now must be on the node2
  disconnect the Nethsecurity instance from the controller
  disconnect the controller from the NethSecurity instance
  try to reconnect the NethSecurity with another join code
  From the connector the NethSecurity is seen registered
  From the NethSecurity the status is seen connected

[gsanchietti]

This is required for sure.

But we need also to try to make the firewall reconnects without reconfiguring them.