The between-set music for Friday night’s homecoming show for DC boys The Walkmen was Big Star. Nothing but Big Star, all the time. About as a fitting as they come for California openers Broken West, who might currently be the most deserving heirs to the tattered power pop crown. They opened with lead single “Down in the Valley,” drawing out the opening, ringing A-chord, double rhythm-guitar parts in classic power pop fashion. Occasionally, the band…