Instead of doing something like

<get caller UID>
if (root) {
   perform_operation()
   other boilerplate stuff
   return;
}

nm_auth_chain_new(perform_operation)
...

just have root also go through the auth chain, which is now
short circuited for root.  This ensures we always use the same
code paths for root and non-root, and that fixes made in one path
are also executed for the other.