Elevate privileges when deleting stack dir

Octavia creates a bunch of files/folders with elevated
privileges in external_post_deploy step. Though we should
ensure the ownership permissions appropriately, it does
not hurt to force delete those with elevated privileges.

Change-Id: I7e8d0a2a1e4a00fcd6cb736919fe0da8f432023c

tripleo_ansible/playbooks/cli-overcloud-delete.yaml

@@ -59,6 +59,7 @@
         path: "{{ config_download_path }}/{{ stack_name }}"
         state: absent
     - name: Remove the deploy stack
+      become: true
       file:
         path: "{{ overcloud_deploy_path }}/{{ stack_name }}"
         state: absent