svn merge -c 1453706 from branch-1 for HDFS-4551. When copying bytes in DatanodeWebHdfsMethods OPEN, use 4096 buffer size to improve performance.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1453709 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c -1453709 for reverting HDFS-4551.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1453710 13f79535-47bb-0310-9956-ffa450edef68