The Bruins fourth line hasn’t been a constant personnel-wise and it hasn’t often been a deciding factor for the Black and Gold during games this season.And it wasn’t a particularly effective group at the end of the road trip out West when the B’s needed all hands on deck, so a strong performance was needed as the team returned home for the first time since before the Christmas holiday.The good news was that Boston’s reconfigured fourth line of Sean Kuraly, Tanner Jeannot and Mark Kastelic popped in a pair of goals in Thursday night’s 4-1 win over the Calgary Flames at TD Garden. Kuraly scored the first goal of the game on a bar down sniper shot and the fourth line was on the ice for Mason Lohrei’s insurance marker in the second period that put Boston up by three goals.