PYEONGCHANG, South Korea (Reuters) - A second Russian athlete has tested positive for a performance-enhancing drug at the Pyeongchang Winter Olympics, a major blow for the nation’s hopes of regaining its Olympic status and drawing a line under years of doping scandals. Bobsledder Nadezhda Sergeeva tested positive for a heart drug on Feb. 18, five days after a previous doping test returned a negative result for her, the Russian bobsleigh federation said in a statement on Friday.