The Henrico County Board of Supervisors did what it does best last night—stuck with what it knows will work. But in doing so, the board broke with a long-standing tradition. On a 4-0 vote with one abstention, the supervisors chose David A. Kaechele to serve a second straight term as chairman. In recent memory, the board’s vice chairman one year has become the chairman the next. But Patricia S. O’Bannon, last year’s vice chairwoman, was passed over in favor of Kaechele.