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

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

Change-Id: Ia964e368c97b17828b38d5d9cd155f79783fcd37

openstack/vitrage-dashboard,openstack/vitrage-dashboard,openstack/vitrage-dashboard,openstack/vitrage-dashboard