Henry R. Kravis has been planning an I.P.O. of his private equity firm for five years. The deal is finally at hand, but the timing is baffling: the stock and credit markets are suffering.Credit...Matthew Staver/Bloomberg News LAST month, as Henry R. Kravis, the co-founder of Kohlberg Kravis Roberts & Company, and his wife, Marie-Josée, took their seats at the Water Cube in Beijing for a session of