So, the Ravens completed their exhibition season with no blemishes on their record, a 5-0 mark, making them the only NFL team to win all their preseason games.Now, before you run out and book plane and hotel reservations for Atlanta, the scene of February’s Super Bowl, consider this fact: The Ravens went unbeaten last exhibition season and the exhibition season before that.And both of the succeeding regular seasons ended with the Ravens out of the playoffs.