Clonezilla: warn while the default share password is in use; prepare-boot-tools.sh no longer fails on an empty tool folder

The final listing of an empty boot-tools/blancco (no Blancco ISO yet)
failed under pipefail and made the script exit 1 after a good download.

playbook/pxe_server_setup.yml

@@ -269,6 +269,16 @@
           Fix it in playbook/site-vars.yml and re-run.
         quiet: yes
 
+    - name: "Clonezilla: WARNING - the default Samba password is in use"
+      # The password is readable from the boot menu by anything on the imaging
+      # LAN and the default is the same at every site. It opens only the
+      # clonezilla share, but each site should set its own.
+      debug:
+        msg: >-
+          !!! WARNING: clonezilla_smb_password is the shipped default. Set a
+          site-specific value in playbook/site-vars.yml and re-run.
+      when: clonezilla_smb_password == "clonezilla-backup"
+
     # --- Re-run safety (nothing below changes the box until these pass) ---
     - name: "Re-run safety: is imaging in progress? (SMB sessions, recent DHCP leases)"
       args: