A couple of weeks ago, Wells Fargo executives — including CEO Timothy Sloan and finance chief John Shrewsberry — were in Washington on unpleasant business. The Federal Reserve planned to impose tough sanctions on the San Francisco bank for years of misconduct and the shoddy governance that allowed it. The executives’ mission, according to three people directly involved in the negotiations, was to avoid further shaking investor confidence in the bank and its management team. Officials at the central bank had a different goal, according to people familiar with their thinking.