Sync latest _i18n module for os_brick

The _i18n module in os_brick is out of date.
It is still using the old oslo.i18n namespace
for the i18n library instead of oslo_i18n.

This patch syncs in the latest incubator code to
correct that.

Current HEAD in OSLO:
---------------------
commit:  9117130d7e73a18f0720ecb264a0a85aa26d3816
Date:  Fri Apr 10 11:39:29 2015 +0200
Test loopingcall and threadgroup on Python 3

Changes merged with this patch:
--------------------------------
0cc741a9 - switch to oslo_i18n

Change-Id: I76d1b2449c75fbd7a4a38bffdbdf492c98f639b1

os_brick/openstack/common/_i18n.py

@@ -17,14 +17,14 @@ See http://docs.openstack.org/developer/oslo.i18n/usage.html
 """
 
 try:
-    import oslo.i18n
+    import oslo_i18n
 
     # NOTE(dhellmann): This reference to o-s-l-o will be replaced by the
     # application name when this module is synced into the separate
     # repository. It is OK to have more than one translation function
     # using the same domain, since there will still only be one message
     # catalog.
-    _translators = oslo.i18n.TranslatorFactory(domain='os-brick')
+    _translators = oslo_i18n.TranslatorFactory(domain='os_brick')
 
     # The primary translation function using the well-known name "_"
     _ = _translators.primary