(Reuters) -Russian steel giant Severstal was racing against the clock on Wednesday to avoid becoming the country’s first major corporate default since the Ukraine crisis began, with international payment lines snarled by sanctions. Severstal, whose main shareholder Alexey Mordashov is one of a number of wealthy Russians now sanctioned by the European Union, has until the end of the day to get an already overdue $12.6 million loan ‘coupon’ payment to its creditors. A source close to the steel firm said the money had been transferred last week but was yet to be processed and passed on by its pay…