UPDATE 3-Obama to fill key posts in weeks, Hagel on Pentagon short-list

* Former Republican senator would give Cabinet bipartisancast * Reshuffle complicated by decision on Hillary Clintonsuccessor WASHINGTON, Dec 4 (Reuters) - President Barack Obama isexpected to announce his nominees for secretaries of state anddefense in the next two weeks, with former Republican SenatorChuck Hagel on the short list of potential choices to head thePentagon, senior administration ...