A rare headed goal by Lionel Messi helped Barcelona beat Manchester United 2-0 in the Champions League final on Wednesday, giving the Spanish side its third European Cup title and third trophy in a magical season.Samuel Eto’o put the Spanish champions ahead in the 10th minute and Messi’s 70th-minute goal – his ninth in the Champions League this season – sealed the victory over the defending champions at the Stadio Olimpico.The triumph completed a sweep of titles for 38-year-old Barcelona coach Pep Guardiola in his first season, after wins in the Spanish league and cup. The former Barcelona star, who started as a ball boy at Camp Nou, now joins the ranks of those who have won the title both as a player and a coach.Guardiola became the youngest coach to win European soccer’s top club competition since the European Cup became the Champions League in 1993. Barcelona also won the trophy in 1992 and 2006.“No team has ever done the treble in Spain, and we’ll be remembered as the first team to do it,” Barcelona striker Thierry Henry said. “That’s amazing.”United had been chasing its fourth European Cup title, and fourth trophy this season after winning the Premier League,…