[SPARK-23159][PYTHON] Update cloudpickle to v0.4.3

## What changes were proposed in this pull request?

The version of cloudpickle in PySpark was close to version 0.4.0 with some additional backported fixes and some minor additions for Spark related things.  This update removes Spark related changes and matches cloudpickle [v0.4.3](https://github.com/cloudpipe/cloudpickle/releases/tag/v0.4.3):

Changes by updating to 0.4.3 include:
* Fix pickling of named tuples cloudpipe/cloudpickle#113
* Built in type constructors for PyPy compatibility [here](cloudpipe/cloudpickle@d84980c)
* Fix memoryview support cloudpipe/cloudpickle#122
* Improved compatibility with other cloudpickle versions cloudpipe/cloudpickle#128
* Several cleanups cloudpipe/cloudpickle#121 and [here](cloudpipe/cloudpickle@c91aaf1)
* [MRG] Regression on pickling classes from the __main__ module cloudpipe/cloudpickle#149
* BUG: Handle instance methods of builtin types cloudpipe/cloudpickle#154
* Fix <span>#</span>129 : do not silence RuntimeError in dump() cloudpipe/cloudpickle#153

## How was this patch tested?

Existing pyspark.tests using python 2.7.14, 3.5.2, 3.6.3

Author: Bryan Cutler <cutlerb@gmail.com>

Closes apache#20373 from BryanCutler/pyspark-update-cloudpickle-42-SPARK-23159.

python/pyspark/accumulators.py

@@ -94,7 +94,6 @@
 else:
     import socketserver as SocketServer
 import threading
-from pyspark.cloudpickle import CloudPickler
 from pyspark.serializers import read_int, PickleSerializer