BZ #1134139 - Track Real User behind SSH logins

Personally I'd rather the absense of a "login" denote either system, application, or unkown ssh keys.  I know it's unlikely someone would have a login be either S or A but it just looks odd to see this in the code.  At the very least we'd need a comment block explaining the reasoning in the code.  @danmcp, did you have an opinion on this?