Let setup.py compile_catalog process all language files

Two years ago the translation files have been split into several
files, separating the log messages of different log levels from each
other, like X.pot, X-log-warning.pot, X-log-info.pot, and so on.
However, the setup.py command `compile_catalogs`, that comes from the
babel package and compiles the corresponding .po files into .mo
files, only supported one file per python package.  This means that
during packaging `compile_catalogs` never compiled the X-log-*.po
files, so the corresponding translations were always missing.

Since babel 2.3 the domain can be set to a space separated list of
domains.  This change adds the the additional log level files to the
domain list.

Change-Id: I436072d03f401240df6d7b8348616bc7c4731c4a
Closes-Bug: #1536226

setup.cfg

@@ -167,7 +167,7 @@ output_file = neutron/locale/neutron.pot
 
 [compile_catalog]
 directory = neutron/locale
-domain = neutron
+domain = neutron neutron-log-error neutron-log-info neutron-log-warning
 
 [update_catalog]
 domain = neutron