It’s the corporate equivalent of ordering too much alcohol for a house party where half the guests turn out to be dry. Except with billions of dollars at stake and a no-returns policy. Distillers’ warehouses are crammed with barrels of aging spirits laid down in better times that fewer people want to drink these days. The problem doesn’t only affect bourbon in the U.S. There is a global glut of cognac, Irish whiskey and Scotch whisky too. Investors tempted by alcohol companies’ low stock-market valuations should look at their saturated balance sheets first.  When aged-spirits distillers are deciding how much…