BOSTON — The Atlanta Hawks seemed to have found the answer to their injury woes: a rejuvenated Tracy McGrady, who was putting together a playoff game reminiscent of his youth. But then McGrady rolled his right ankle, crumpled to the ground and limped off the court. Although he returned in the second half, he did not make another basket and the Celtics held on to beat the depleted Hawks 90-84 in overtime Friday night to take a 2-1 lead in the best-of-seven series.