IZU, Japan—With a glorious sense of under-statement Jason Kenny said he had just kept “chipping away” over more than a decade of track cycling domination to become Britain’s most successful Olympian. By not just beating, but absolutely smashing the opposition, in the keirin final at the Izu Velodrome on Sunday, the 33-year-old Kenny earned a seventh Olympic gold medal. That put him one above former track team mate Chris Hoy with whom he previously shared the record. “It’s special to get a gold medal still at the end of the day,” the modest Kenny told reporters after cementing his place as one of the greatest British athletes of all time. “I just keep chipping away really, keep turning up and getting stuck in.” Kenny, who swept the sprints and keirin in Rio said he had questioned whether he still had the power to compete with the likes of flying Dutchman …