East Tennessee has a 12-pack of twisty routes mapped for motorcyclists.  These Southern Dozen, created by the Johnson City Convention & Visitors Bureau, range in length from 37 miles to 157 miles. They trace Appalachian Country roads through switchbacks and scenery. In late May, four of us spent three days riding the routes. And, that wasn’t nearly enough time.  While logically we could have ridden all 1,132 miles in three days, we would have skipped waterfalls, panoramic views, a rich micro-beverage culture, bluegrass music and good ole Southern comfort food. Next time, we’ll plan a longer stay in Johnson City, Tenn., the alpha and omega of Southern Dozen routes. And, we’ll pack our bathing suits. The Carnegie Hotel there boasts a heated, salt water…