(Adds detail from event, comments from Cancellara, Froome) By Martyn Herman RIO DE JANEIRO, Aug 10 (Reuters) - Swiss Fabian Cancellara rode off into a golden retirement with a second Olympic time trial title after a masterful ride that eclipsed Tour de France champion Chris Froome on Wednesday. Froome had been fancied for victory on a hilly 54.5km circuit that looked made for the Briton, but Cancellara, the man they call Spartacus, was in a league of his own as he nailed the last time trial of his 16-year career. Dutchman Tom Dumoulin, whose place had been in jeopardy after breaking his wrist on the Tour de France, was second. More...