Unify different names between Python2/3 with six.moves

Some modules use different names in Python2 and Python3. Use six.moves
to make them work well in Python2 and Python3.
This is changes mapping:

six.moves      Python 2                 Python 3
builtins        __builtin__ 	        builtins
filter 	       itertools.ifilter() 	filter()
reduce 	       reduce() 	        functools.reduce()
reload_module  reload() 	        imp.reload()

Implements: blueprint make-python3-compatible
Change-Id: I97971f2ab40385bfc2c73ae7e8a7620c4d64a03c
Merge "Unify different names between Python2/3 with six.moves"