MINOR: http-rules: Use an action function to eval http-request auth rules

MINOR: http-rules: Use an action function to eval http-request auth rules

Now http-request auth rules are evaluated in a dedicated function and no longer
handled "in place" during the HTTP rules evaluation. Thus the action name
ACT_HTTP_REQ_AUTH is removed. In additionn, http_reply_40x_unauthorized() is
also removed. This part is now handled in the new action_ptr callback function.