(Reuters) - If there's a way to dilute the bitterness in relations between Russia and Georgia after a 2008 war, it may lie in a lush valley south of the Caucasus Mountain border between the feuding former Soviet republics. Here flows Borjomi, a naturally carbonated mineral water of volcanic origin that had been popular in Russia since the 19th century until it was swept off the shelves when Moscow banned Georgian beverages and other products in 2006 as tensions built toward the five-day war.