What’s behind the August sell-off? Goldman Sachs economists see an end to the Fed’s hawkish policy on interest rates, predicting that the central bank will cut its prime lending rate in the second quarter of next year. But that bullish prediction is doing little to restore investors’ optimism, as concerns mount about consumer confidence and the health of global economy. China’s woes are reverberating. The country, a major engine of growth, has been rocked by a decline in trade, a slowdown in consumer spending, a crackdown on the private sector…