* Schurter wins gold after near-miss in London * Sagan suffers mechanical issues * Kulhavy settle for bronze (Adds quotes, details) By Martyn Herman RIO DE JANEIRO, Aug 21 (Reuters) - Switzerland's Nino Schurter left nothing to chance this time as he completed his full set of Olympics medals by beating Czech Jaroslav Kulhavy for gold in the men's cross-country cycling race on Sunday. All eyes had been on Slovakia's world road race champion Peter Sagan at the start after his surprise decision to contest the mountain bike event rather than go for gold on tarmac. More...