Drop use of 'oslo' namespace package

The Oslo libraries have moved all of their code out of the 'oslo'
namespace package into per-library packages. The namespace package was
retained during kilo for backwards compatibility, but will be removed by
the liberty-2 milestone. This change removes the use of the namespace
package, replacing it with the new package names.

The patches in the libraries will be put on hold until application
patches have landed, or L2, whichever comes first. At that point, new
versions of the libraries without namespace packages will be released as
a major version update.

Please merge this patch, or an equivalent, before L2 to avoid problems
with those library releases.

Blueprint: remove-namespace-packages
https://blueprints.launchpad.net/oslo-incubator/+spec/remove-namespace-packages

Change-Id: I1fd9eba88ec8d436f6d2e37df851dbaa84a8c78c

glance_store/_drivers/filesystem.py

@@ -26,8 +26,8 @@ import stat
 import urlparse
 
 import jsonschema
-from oslo.serialization import jsonutils
 from oslo_config import cfg
+from oslo_serialization import jsonutils
 from oslo_utils import excutils
 from oslo_utils import units