Update translation setup

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.db/locale/oslo.db.pot to
oslo_db/locale/oslo_db.pot.
For this we need to update setup.cfg.

Update also domain name in _i18n.py.

Change-Id: I5b3052f840201557f3b1c85effeda3bb3318a9ee

oslo_db/_i18n.py

@@ -19,7 +19,7 @@ See http://docs.openstack.org/developer/oslo.i18n/usage.html .
 import oslo_i18n
 
 
-_translators = oslo_i18n.TranslatorFactory(domain='oslo.db')
+_translators = oslo_i18n.TranslatorFactory(domain='oslo_db')
 
 # The primary translation function using the well-known name "_"
 _ = _translators.primary

setup.cfg

@@ -73,18 +73,18 @@ all_files = 1
 upload-dir = doc/build/html
 
 [compile_catalog]
-directory = oslo.db/locale
-domain = oslo.db
+directory = oslo_db/locale
+domain = oslo_db
 
 [update_catalog]
-domain = oslo.db
-output_dir = oslo.db/locale
-input_file = oslo.db/locale/oslo.db.pot
+domain = oslo_db
+output_dir = oslo_db/locale
+input_file = oslo_db/locale/oslo_db.pot
 
 [extract_messages]
 keywords = _ gettext ngettext l_ lazy_gettext
 mapping_file = babel.cfg
-output_file = oslo.db/locale/oslo.db.pot
+output_file = oslo_db/locale/oslo_db.pot
 
 [pbr]
 warnerrors = True