fix(proxmox_lxc_provision): post-clone privilege escalation and SSH key regen var name

The user-module tasks in post-clone.yml were running without become, so
modifying /etc/passwd failed with 'usermod: Permission denied' when the
connection user (e.g. admin) was non-root. Add become: true to both
password tasks. Block-level become is avoided because the known_hosts
task in the same file is delegate_to: localhost and should not sudo on
the controller.

Also fix the variable name passed to the system_setup ssh tasks_from:
post-clone.yml was setting 'regenerate_ssh_keys', but ssh.yml gates on
'regenerate_ssh_host_keys'. The mismatch caused cloned containers to
silently keep the source template's SSH host keys.

roles/proxmox_lxc_provision/tasks/post-clone.yml

@@ -4,6 +4,7 @@
     name: root
     password: "{{ lxc_root_password | password_hash('sha512') }}"
     update_password: always
+  become: true
   when: lxc_root_password is defined
 
 - name: Change user password
@@ -11,6 +12,7 @@
     name: "{{ lxc_user_name }}"
     password: "{{ lxc_user_password | password_hash('sha512') }}"
     update_password: always
+  become: true
   when: lxc_user_password is defined
 
 - name: Regenerate SSH host keys
@@ -18,7 +20,7 @@
     name: system_setup
     tasks_from: ssh
   vars:
-    regenerate_ssh_keys: true
+    regenerate_ssh_host_keys: true
 
 - name: Remove previous entry from known hosts
   ansible.builtin.known_hosts: