RHOSP16 Protecting the overcloud stack from removal does not work

Issue

In the past, the 16.x documentation for protecting the overcloud from removal was not functional.

• Adding {"stacks:delete": "rule:deny_everybody"} in the config file /var/lib/config-data/puppet-generated/heat/etc/heat/policy.json does not prevent it from being deleted accidentally.

  # with {"stacks:delete": "rule:deny_everybody"} in the wrong policy.json file ...
  
  (undercloud) [stack@undercloud-0 ~]$ openstack overcloud delete overcloud
  Are you sure you want to delete this stack(s) [y/N]? y
  Request to delete stack overcloud has been accepted.