When Billy Joel visited the Soviet Union for a series of historic concerts in 1987, he learned it was still rock ‘n’ roll to them — albeit slightly different. On July 26, 1987, Joel and his band played at the Olimpiyskiy Stadium in Moscow to kick off a six-show “tour,” making him the first Western artist to take a full-blown stage production behind the then-wilting Iron Curtain. With three concerts each in Moscow and Leningrad (now St. Petersburg), it was a triumphant and only occasionally troubled bit of international diplomacy, ultimately leaving Soviet fans dancing, twisting and shouting in…