Fix image-download to stdout on Python 3.x
Fix image-download to stdout on Python 3.x

Glance image-download to stdout fails on Python3 due to sys.stdout.write
not allowing bytes to be written directly.

A good description of the issue is listed at http://bugs.python.org/issue18512

Closes-Bug: #1528083

Change-Id: I2963914e2e0744410267b5735ff77939413916d4

klmitch/python-glanceclient,klmitch/python-glanceclient,openstack/python-glanceclient,openstack/python-glanceclient