Follow new infra setup for translations, see spec
http://specs.openstack.org/openstack-infra/infra-specs/specs/translation_setup.html
for full details.
This basically renames
oslo.messaging/locale/oslo.messaging.pot to
oslo_messaging/locale/oslo_messaging.pot. For this we need to update
setup.cfg.
Update also domain name in i18n.py.
Change-Id: Idf5300224f572d29953261ac998e7bf32a12822d