By Julien Pretot, Gabrielle Tétrault-Farber and Chang-Ran Kim BEIJING (Reuters) -Russian teenager Kamila Valieva dominated the Olympic ice on Tuesday night, fighting back tears as she completed a skate that put her at the top of the short programme standings with a doping cloud hanging over her. The 15-year-old has been engulfed by a doping scandal in Beijing, but was cheered by spectators as she took to the ice for first time since news of her failed drugs test. For two minutes and 40 seconds, millions around the world watched her every move, her music, In Memoriam by Kirill Richter, almost d…