By Pratima Desai LONDON (Reuters) – Hedge fund Elliott Associates and Jane Street Global Trading are suing the London Metal Exchange for up to $500 million after the LME cancelled nickel trades on March 8 when prices soared to record highs above $100,000 a tonne in chaotic trade. The nickel trading debacle is the biggest crisis to hit the world’s oldest metals forum in decades. Suspension of trading on March 8 left consumers and producers without key benchmark prices and damaged the 145-year-old LME’s reputation. Sources familiar with the events around the suspension said that if the LME hadn’…