Change openstack-dev to openstack-discuss
Change openstack-dev to openstack-discuss

Mailinglists have been updated. Openstack-discuss replaces openstack-dev.

Change-Id: Ic18dd083253d1aa0507afe223de1886bec0b700e

openstack/magnum-ui,openstack/magnum-ui,openstack/magnum-ui,openstack/magnum-ui