svn merge -c 1461040 from trunk for HDFS-4598. Fix the default value of ConcatSourcesParam and the WebHDFS doc.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1461042 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1461146 FIXES: MAPREDUCE-4875. coverage fixing for org.apache.hadoop.mapred (Aleksey Gorshkov via bobby)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1461149 13f79535-47bb-0310-9956-ffa450edef68