Update mailinglist from dev to discuss
Update mailinglist from dev to discuss

openstack-dev was decomissioned this night in https://review.openstack.org/621258
Update openstack-dev to openstack-discuss

Change-Id: I162a2b44703cf8994b482b9efeabf6ad812181f8

openstack/openstack-ansible-apt_package_pinning,openstack/openstack-ansible-apt_package_pinning