Just this week, Andrew Leahey & the Homestead played 10 gigs over five days aboard the annual Rock Boat cruise, including one on the main deck stage in the pounding rain. Such marathon schedules are par for the course for Leahey, a Virginia native, Nashville resident and occasional Rolling Stone contributor who has made it his mission to revive heartland rock & roll. On his new single, “Airwaves,” he celebrates the power of the genre and champions the still-influential medium of radio…