[SPARK-791] [PySpark] fix pickle itemgetter with cloudpickle

fix the problem with pickle operator.itemgetter with multiple index.

Author: Davies Liu <davies.liu@gmail.com>

Closes #1627 from davies/itemgetter and squashes the following commits:

aabd7fa [Davies Liu] fix pickle itemgetter with cloudpickle

(cherry picked from commit 92ef02626e793ea853cced4cbfee316f0b748ed7)

Conflicts:
	python/pyspark/tests.py