One so seldom has the opportunity to report good news about labor unions that when two good things happen in the space of 24 hours that’s a triumph. The first is a rebuke to the incoming Trump administration. The second is an unacknowledged favor to it (but, more importantly, to the nation as well). Item One is that the Service Employees International Union, reversing a bad decision 20 years ago to disaffiliate with the AFL-CIO, is rejoining the…