Dr. Donald Berwick was already in Massachusetts when I spoke to him Sunday afternoon. He was back in the Newton home where he’d lived for 30 years, being pleasantly interrupted during our conversation by his 2-year-old grandson. His last day in Washington as the administrator of the Centers for Medicare and Medicaid Services had been Thursday. Friday was packing day. Saturday was moving day. And, by Sunday, he was already talking about his too-short, 17-month tenure as the nation’s top Medicare official in the past tense. Which, alas, it was.