Transition to Neutron project in Launchpad

Gracefully handle the Launchpad project rename from Quantum to Neutron,
by redirecting changes to not-yet-renamed openstack/quantum repo to the
already-renamed "neutron" LP project (same for python-*client projects).

This should be accepted once the following LP support request is done:
https://answers.launchpad.net/launchpad/+question/231396

Change-Id: Ib47970716d6aef54d6a641bb78f966d5feb1e3bb
Reviewed-on: https://review.openstack.org/34549
Reviewed-by: James E. Blair <corvus@inaugust.com>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins