Faster shopfloor-setup sync, prompt spacing, XP-era test client

- Deploy shopfloor-setup with rsync instead of the copy module: the
  ~4 GB tree took about 4 minutes on every re-run because copy checksums
  each file. rsync transfers only changes; changed only when it did.
- iPXE drops a trailing space, so 'Machine number:' ran into the typed
  digits. The space now comes from a hex 20 setting.
- tests/vm: pxetest-xp is a permanent client (SeaBIOS, qemu32 32-bit CPU,
  rtl8139, 1 GiB, IDE disk) for the i686 Clonezilla path; start.sh xp.
  Only one client may run at a time across all three.

playbook/pxe_server_setup.yml

@@ -986,12 +986,20 @@
       ignore_errors: yes
 
     - name: "Deploy shopfloor setup scripts to enrollment share"
-      copy:
-        src: "{{ usb_mount }}/shopfloor-setup/"
-        dest: /srv/samba/enrollment/shopfloor-setup/
-        mode: '0755'
-        directory_mode: '0755'
-      ignore_errors: yes
+      # rsync, not copy: the tree is ~4 GB and the copy module checksums every
+      # file one by one, so a re-run spent minutes here. rsync compares size
+      # and mtime and transfers only what changed. Merge, no --delete: files
+      # a site added on the share stay. Skipped if the USB has no tree.
+      shell: |
+        set -euo pipefail
+        SRC="{{ usb_mount }}/shopfloor-setup/"
+        [ -d "$SRC" ] || { echo "SKIP: no shopfloor-setup on the USB"; exit 0; }
+        mkdir -p /srv/samba/enrollment/shopfloor-setup
+        rsync -rlt -i --chmod=D0755,F0755 "$SRC" /srv/samba/enrollment/shopfloor-setup/
+      args:
+        executable: /bin/bash
+      register: shopfloor_rsync
+      changed_when: shopfloor_rsync.stdout | trim | length > 0 and 'SKIP:' not in shopfloor_rsync.stdout
 
     - name: "Deploy preinstall.json to pre-install/"
       copy: