HDFS-6982. nntop: top­-like tool for name node users. (Maysam Yabandeh via wang)

(cherry picked from commit dcb8e24427b02e2f3ff9a12d2eb1eb878e3443bb)
HDFS-7404. Remove o.a.h.hdfs.server.datanode.web.resources. Contributed by Li Lu.