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: I40e2f7f7cff547fc46e32712f9f7c27cc3ae14ee

openstack/openstack-ansible-rsyslog_client,openstack/openstack-ansible-rsyslog_client