WASHINGTON Sergey Kislyak, Russia’s long-serving ambassador to the United States, has a habit noticed by many U.S. officials who have known the envoy. “He doesn’t get as much credit as he should, in my view, for being savvy about developing relationships with people all over the city,” said Michael McFaul, who knew the diplomat well while serving in the Obama administration as senior adviser on Russia and then as U.S. ambassador to Russia.