aci-update: Add ACI for read-only admin attributes
Most admin access is granted with the "Admin can manage any entry" ACI,
but before the global anonymous read ACI is removed, read-only admin
access must be explicitly given.
Add an ACI for read-only attributes.
https://fedorahosted.org/freeipa/ticket/4319
Reviewed-By: Martin Kosek <mkosek@redhat.com>