HDFS-7424. Add web UI for NFS gateway. Contributed by Brandon Li

(cherry picked from commit 1bbcc3d0320b9435317bfeaa078af22d4de8d00c)
YARN-2301. Improved yarn container command. Contributed by Naganarasimha G R
(cherry picked from commit 258623ff8bb1a1057ae3501d4f20982d5a59ea34)
HADOOP-11348. Remove unused variable from CMake error message for finding openssl (Dian Fu via Colin P. McCabe)
(cherry picked from commit 565b0e60a8fc4ae5bc0083cc6a6ddb2d01952f32)