There are some operations, like those for the certificate system, that
don't need to write to the directory server. So instead we have an entry
that we test against to determine whether the operation is allowed or not.
This is done by attempting a write on the entry. If it would succeed then
permission is granted. If not then denied. The write we attempt is actually
invalid so the write itself will fail but the attempt will fail first if
access is not permitted, so we can distinguish between the two without
polluting the entry.
