BERLIN/ATHENS (Reuters) - Greece's foreign lenders hailed a bond buyback as a success even though it narrowly fell short of a target to cut the country's debt, paving the way for Athens to get long-delayed aid to avoid bankruptcy. The scheme was intended to put Greece's debt mountain on a more sustainable footing but is now expected to cut it by less than initially hoped because of higher-than-expected prices to buy back the bonds. To make up the shortfall, Athens asked its foreign lenders for an extra 1.29 billion euros over the 10 billion euros initially allotted to buy back all the 31. ...