BUG: add a test to demonstrate ThreadedIteratorPartitioner bug

Change-Id: Ic9eb9b2026bef51756c87340bb113a49438c3c81
BUG: IteratorPartitioner extra thread don't advance

Under several circumstances, a thread could not be used. However the
threads range could be advanced past the end or the iterator
range. Consider the case with 22 elements and 8 threads. ceil(22/8) =
4, so thread 0: gets 0-3, 1:4-7,...,5:20-22, So thread 6 and 7 are not
used. The last thread would be iterate past the end all the way to 28,
causing likely abnormal program termination.

Change-Id: I7ca8d60c2eed6237f56b5eb03f825cabaa37a596
Merge topic 'FixThreadedIteratorPartitioner'

d284699 BUG: IteratorPartitioner extra thread don't advance
753c12e BUG: add a test to demonstrate ThreadedIteratorPartitioner bug