By Kirstin Ridley LONDON (Reuters) -A second man convicted in Britain over how oil contracts were secured in post-occupation Iraq has had his conviction overturned by a London court, further unravelling a blockbuster bribery case prosecuted by the UK Serious Fraud Office (SFO). Paul Bond, 69, received a three-and-a-half-year jail sentence last March after an investigation into how Monaco-based oil consultancy Unaoil won contracts for Western clients in the Middle East, Central Asia and Africa. But the former manager at Dutch energy services company SBM Offshore launched an appeal after the Cou…