Find transaction ids for internal redirects
    
    On internal redirections, such as when ErrorDocument is used to
    redirect on failed negotiate authentication we need to look harder
    for the transaction id.
    
    Ticket: #74
    
    Signed-off-by: Simo Sorce <simo@redhat.com>
    Reviewed-by: Nathan Kinder <nkinder@redhat.com>