HADOOP-9154. SortedMapWritable#putAll() doesn't add key/value classes to the map. (Karthik Kambatla via tgraves)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1446271 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-0.23' into branch-0.23-gd
Merge remote branch 'origin/branch-0.23-gd' into fb-HADOOP-9078-branch-0.23-gd