Add openstack/placement as a repo on #openstack-placement
Add openstack/placement as a repo on #openstack-placement

That repo now exists. For the time being the #openstack-placement
channel will report changes for nova and placement. Later some
nova changes will be removed.

Change-Id: Ie29bec70bdc9f43d612ece33c1231140a6a15b65

openstack-infra/project-config,openstack-infra/project-config