MAPREDUCE-980.  Modify JobHistory to use Avro for serialization.
MAPREDUCE-980.  Modify JobHistory to use Avro for serialization.

git-svn-id: b802f630c9bf5b8d3a5502364db61db7aee7af4a@816801 13f79535-47bb-0310-9956-ffa450edef68

apache/mrunit,apache/mrunit,apache/mrunit