By Manya Saini (Reuters) -Navan's shares started trading 12% below their initial public offering price on Thursday, as the travel technology company faced choppy market conditions amid a prolonged U.S. government shutdown. Momentum in the U.S. IPO market, which ​had picked up pace in the second half of the year after a years-long lull, stalled at the start of October when the U.‌S. markets regulator furloughed staff and paused the review of filings. The Securities and Exchange Commission later eased res ...