The Boston Bruins seemed to have a fire lit under them in Game 5 of their first-round playoff series against the Ottawa Senators. And it might have been the Sens’ own fault. The Bruins were able to win to pick up the 3-2 win in overtime Friday after falling behind 2-0 in the second period while facing elimination. But Boston coach Bruce Cassidy thought it might’ve had something to do with what was said to David Krejci after the Bruins forward took a knee-on-knee hit from Senators defenseman Chris Wideman at the end of the opening period. “I think when the hit on Krejci, when they started chirping (Krejci), I think