Teach subunit2html to use v2 when it is available.
Teach subunit2html to use v2 when it is available.

This changes the API of the result object to be more standard with
Python2.7+ APIs.

Change-Id: I1dd3da2280d687a591efd069ef43b1f2bc40e9f1
Reviewed-on: https://review.openstack.org/23670
Reviewed-by: Clark Boylan <635fc31d01fa593720982fa0568e87170cedbe2c@gmail.com>
Approved: Monty Taylor <37c07a49ee3d5191376d758eb1d8298b34456b8e@inaugust.com>
Reviewed-by: Monty Taylor <37c07a49ee3d5191376d758eb1d8298b34456b8e@inaugust.com>
Tested-by: Jenkins

open-switch/infra_puppet-jenkins,open-switch/infra_puppet-jenkins