The Bruins may be locked into second place in their division, but they still should be trying to pick up these last four points. From the Playoff Page at NHL.com:
Blockquote In the Conference Finals and Stanley Cup Final, home-ice advantage goes to the team that had the better regular-season record – regardless of the teams’ final standing in their respective divisions.
That means that if the Bruins finish the regular season ahead of Calgary and Washington then they would have Home Ice Advantage against those two teams (and everyone else), should they manage to win their first two playoff rounds.