We had been looking forward to seeing Swedish indie darlings Peter Bjorn and John for some time, but as sometimes happen with indie darlings, Monday’s sold out 9:30 Club show underwhelmed. The trio, who have been all over Pitchfork and the blogs, play understated, finely crafted 60s-ish pop. They’ve been together since 1999, but their third album, 2006’s “Writer’s Block,” catapulted them to indie stardom, mainly due to the single “Young Folks.” The rest of…