Make makemessage ignore option work with Django 1.6

In run_tests.sh --makemessages, files under openstack/common are excluded
and "--ignore=openstack/common" option to manage.py makemessages is used
to exclude these files. However, after the default version of Django is
switched to 1.6, "--ignore" option works does not work as previously it
does and strings from openstack/common are included in translation strings.

The reason of this is that ignore pattern is checked against basename of
each file/directory in Django 1.6. We need to specify basename in ignore
patterns: i.e. --ignore=openstack. At now we don't have directories named
as "openstack" other than openstack_dashboard/openstack/common, so it works.

This works both with Django 1.6 and 1.5.

Change-Id: I547be679c2f4ce49bd439b8f629e8720eebdb896
Closes-Bug: #1295920
Merge "Make makemessage ignore option work with Django 1.6"