Remove graduated gettextutils from openstack/common

Use oslo.i18n package and handle different versions properly in
glanceclient._i18n. The oslo namespace is being deprecated so imports
will be oslo_i18n going forward. For older versions of oslo.i18n though,
we will still be able to import i18n from oslo.

Change-Id: Id56d34ccf447dc6f7becafb74d6a30e8a1642030

requirements.txt

@@ -11,3 +11,4 @@ requests>=2.2.0,!=2.4.0
 warlock>=1.0.1,<2
 six>=1.7.0
 oslo.utils>=1.2.0                       # Apache-2.0
+oslo.i18n>=1.3.0  # Apache-2.0