HIVE-4516 : Fix concurrency bug in serde/src/java/org/apache/hadoop/hive/serde2/io/TimestampWritable.java (Jon Hartlaub and Navis via Ashutosh Chauhan)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1489673 13f79535-47bb-0310-9956-ffa450edef68