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: I75b85386a6ddc53dd097a6dfa44bca60ce2e3d5d

openstack/openstack-ansible-pip_install,openstack/openstack-ansible-pip_install