MAPREDUCE-4953. HadoopPipes misuses fprintf. (Andy Isaacson via tgraves)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1442609 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4462. 2NN will fail to checkpoint after an HDFS upgrade from a pre-federation version of HDFS. (atm)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1442620 13f79535-47bb-0310-9956-ffa450edef68
Merge branch 'branch-0.23' of github.com:griddynamics/yhadoop-common into branch-0.23-gd