Fix message-authenticator attribute check for rfc 5997

[Alan DeKok]

Frederic Leroy wrote:
> On Mon, Jun 27, 2011 at 01:09:39PM +0200, Alan DeKok wrote:
>>   I've put a better fix into git.
> 
> The patch don't work for me, I tested it ... sorry.

  Oh, stop it.

  Give *useful* information.  If you're not going to do that, there's no
point in sending a content-free message.

  Alan DeKok.