build universal wheels
build universal wheels

By default setuptools produces a version-specific wheel file so
installation under other versions of Python require extra work at
install time. This change turns on "universal" wheel support, so that
the wheel file will be marked as supporting both Python 2 and 3.

Change-Id: I00bc3d736e87bcc3a122b688c5e10e82b1b03d84
Signed-off-by: Doug Hellmann <0798ebecfb7bc4dfb9d0445c2fa030eb64e1fa1c@doughellmann.com>

openstack/neutron-lib,openstack/neutron-lib,openstack/neutron-lib,openstack/neutron-lib