As Russell McMurry of Hall County was getting sworn in Jan. 20 as Georgia Department of Transportation’s new planning director, the revolving door that is that department’s top job swung again. That same day, the State Transportation Board voted to promote him to a new and much more challenging job: DOT commissioner. It marked another unusual chapter for a job that has changed hands six times in 15 years, with a sprinkling of interim commissioners in-between.