By Samuel Shen and Xie Yu HONG KONG/SHANGHAI (Reuters) – China’s securities regulators are gathering information from futures brokerages about their clients’ short positions in nickel to prevent spillover risks from rocketing prices this week, three people with knowledge of the matter said on Thursday. The London Metal Exchange intervened on Tuesday to calm the nickel market after prices hit records of more than $100,000 a tonne as Western sanctions threatened supply from major producer Russia. In China, the Shanghai Futures Exchange suspended nickel trading on Thursday after the metal surged …