add python 3.6 unit test job
add python 3.6 unit test job

This adds a unit test job running under Python 3.6 as part of the
python3-first goal. See the python3-first goal document for details:
https://governance.openstack.org/tc/goals/stein/python3-first.html

This is manually generated because the script doing this for other
projects does not currently handle the neutron special case.

Change-Id: I92e7b79df29031b6d94d6ab93305f4e20c1ec3a1
Story: #2002586
Task: #24324

stackforge/neutron-powervm,openstack/networking-powervm,stackforge/neutron-powervm,openstack/networking-powervm