Python style/portability fix

Python style/portability fix

In practice, one would normally explicitly derive a class from
object class (was called new-style class back then).
https://docs.python.org/release/2.5.2/ref/node33.html
https://wiki.python.org/moin/NewClassVsClassicClass

print needs parentheses for portability with Python3.x.

xrange() only exists in Python2.x (i.e. breaks on Python3.x).
Using range() (which pre-allocates a whole list in Python2.x)
won't be a problem unless len(averages) is huge enough to give
any pressure to vm subsystem.

Signed-off-by: Tomohiro Kusumi <tkusumi@tuxera.com>
Signed-off-by: Jens Axboe <axboe@fb.com>