CANADA STOCKS-TSX rises as investors brace for Fed

* TSX up 27.98 points, or 0.18 percent, at 15,510.54 * Eight of the 10 main index sectors advance * Energy stocks rise with price of oil By John Tilak TORONTO, Sept 16 (Reuters) - Canada's main stock index edged higher on Tuesday, driven by gains in most major sectors as investors nervously awaited the outcome of a key U.S. Federal Reserve policy meeting. The market expects the Fed to provide more clarity on interest rates at the end of a two-day policy meeting on Wednesday,