HIVE-8322: VectorReduceSinkOperator: ClassCastException: ~StandardUnionObjectInspector cannot be cast to ~IntWritable (Matt McCline reviewed by Prasanth Jayachandran)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/branch-0.14@1629273 13f79535-47bb-0310-9956-ffa450edef68