Neutron versions api now has its own middleware pipeline
Neutron versions api now has its own middleware pipeline

This patch exposes the root (version) resource to CORS-enabled
browser clients that wish to perform API version discovery. It
does this by creating a new composite pipeline for the neutronversions
app, adding the already-existing CORS middleware into the chain.

This feature is required for js-openstack-lib, and its devstack
tests. https://review.openstack.org/#/c/366905/

Change-Id: I6611839f38d553fc29c813a4b8d874fde77b8034
required-by: Ia2f59213eedf6d7acbb02789ee921c13ff391d09

mahak/neutron,cloudbase/neutron,mahak/neutron,huntxu/neutron,eayunstack/neutron,eayunstack/neutron,openstack/neutron,openstack/neutron,noironetworks/neutron,noironetworks/neutron,sebrandon1/neutron,cloudbase/neutron,openstack/neutron,huntxu/neutron,sebrandon1/neutron,mahak/neutron