CLEVELAND — Before taking the floor, LeBron James stood in the hallway with his teammates outside Cleveland’s locker room and pounded his chest with both hands. The Celtics got thumped next. James had 27 points and 12 assists, Kevin Love added 14 rebounds and the Cavaliers looked like a different team on their home court, tightening the Eastern Conference finals with a 116-86 victory in Game 3 over Boston on Saturday night. Outplayed during two losses in Boston, the Cavs used a three-day break in the series to regroup and re-grip this series.