By Jonathan Stempel NEW YORK (Reuters) – A U.S. appeals court on Wednesday overturned the conviction of a former Chinese diplomat and head of U.S. operations for a Chinese construction company for engaging in forced labor, while upholding his conviction on two other charges. Citing improper testimony from a government expert on forced labor, the 2nd U.S. Circuit Court of Appeals in Manhattan ordered a new trial for Dan Zhong on three counts related to his allegedly having forced workers into “debt bondage” contracts. Zhong, 52, has been serving a 190-month prison term–nearly 16 years–followi…