Global central bankers, eager to see the economy stand on its own feet, faced the rude reality this week of market turmoil threatening already faltering growth and prolonging world reliance on easy money. When stock markets turned south last week after rallying for much of this year, many policymakers initially played that down. “It reminds me of the massive flight to quality we saw during the (2008) banking crisis, when there were fears that the whole global economy would tip into depression,” said Nick Stamenkovic, a strategist at Edinburgh-based RIA Capital Markets.