[SPARK-17773] Input/Output] Add VoidObjectInspector

## What changes were proposed in this pull request?
Added VoidObjectInspector to the list of PrimitiveObjectInspectors

## How was this patch tested?

(Please explain how this patch was tested. E.g. unit tests, integration tests, manual tests)
Executing following query was failing.
select SOME_UDAF*(a.arr)
from (
select Array(null) as arr from dim_one_row
) a

After the fix, I am getting the correct output:
res0: Array[org.apache.spark.sql.Row] = Array([null])

Author: Ergin Seyfe <eseyfe@fb.com>

Closes #15337 from seyfe/add_void_object_inspector.