[reSIProcate] What to do about missing auth tags?

[bcampen]

    When Auth.cxx can't find an auth tag, it throws an exception, which 
the various authentication functions in Helper.cxx do not catch (in 
fact, this exception will make it all the way back up to DumThread 
before it is caught.) I want to fix this, although I want to hear back 
about whether this should be caught in Helper, or higher up in 
ServerAuthManager::handle(msg). I think sending a 400 if something goes 
wrong in handle() is a bit presumptuous, so it looks like it would be 
more correct to catch the problem in Helper, and return BadlyFormed. 
Maybe we should also put a try block around handle() that will send a 
500 response if some unknown thing goes wrong. Anyone have an opinion on 
this?

Best regards,
Byron Campen