Russian Daniil Medvedev finished the tennis season in London on Sunday with a 4-6, 7-6 (7-2), 6-4 triumph against Austria’s Dominic Thiem to lift the ATP Finals trophy inside an empty O2 Arena. Thiem, who lost last year’s ATP final to Greece’s Stefanos Tsitsipas, clinched the first set by a single break after he survived two early break points from Medvedev’s determined rallying.Medvedev fought back from 2-0 behind in the second set tiebreak to level the scoreboard and collected a decisive…