Over the past year, the owner of the Tropicana casinos in Las Vegas and Atlantic City has alienated regulators and politicians, upset lenders and agitated labor unions and employees. But last week’s appointment of Scott Butera as president of Tropicana Entertainment is the most dramatic sign yet the company is starting to patch up relationships with regulators and business associates while attempting to shore up performance at its casinos in Nevada and other states that have lost ground to competitors.