Dropkick Murphys made their first Summerfest appearance Friday night and it's not a reach to say it won't be their last. The Boston-based Celtic punk outfit, which has developed a devoted local following with frequent visits and sweat-drenched shows in tiny clubs all the way up to the Eagles Ballroom, played an energetic 90-minute set before a jam-packed house at the Harley-Davidson Roadhouse.