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: I1bae3d1a1ee788889aa4784c61fc989c71d0e426

openstack/openstack-ansible-rsyslog_server,openstack/openstack-ansible-rsyslog_server