FRANKFURT — The name MG used to be synonymous with spirited but finicky sports cars from Britain. Nowadays the iconic octagonal badge serves a different kind of motoring ambition: China’s push to become a big player in the global auto market. SAIC Motor, one of China’s Big Four automakers, bought the MG brand in 2007 and is stamping it on a line of electric sport utility vehicles on sale in Germany and other European markets. MG is an example of how Chinese carmakers are exploiting the shift to electric cars…