HILTONS, Va. — The lives of A.P., Maybelle and Sara Carter, their music and the historic Bristol Sessions are brought to life in “Keep on the Sunny Side,” which premiered in 2002 at the Barter Theatre in Abingdon, Va.Not only was it performed many times there, “Keep on the Sunnyside” was also presented multiple times at the Carter Fold.And, next weekend, the production returns to “The Fold.”The Carter Family Fold will host six performances of “Keep on the Sunny Side” between May 28 and June 7.