By Eric Onstad and Pratima Desai LONDON (Reuters) – Commodity trader Trafigura and other firms are moving to take large amounts of zinc out of London Metal Exchange approved warehouses in Asia, sources familiar with the matter said, fuelling concern about more problems at the exchange after chaotic nickel trading last month. A Trafigura spokesperson in response to request for comment said “we don’t usually comment on commercial matters”. The LME, the world’s biggest market for industrial metals, suspended nickel trading on March 8 and cancelled billions of dollars in trades after prices spiked…