Use oslo-config-2013.1b4

The cfg API is now available via the oslo-config library, so switch to
it and remove the copied-and-pasted version.

Add the 2013.1b4 tarball to tools/pip-requires - this will be changed
to 'oslo-config>=2013.1' when oslo-config is published to pypi. This
will happen in time for grizzly final.

Add dependency_links to setup.py so that oslo-config can be installed
from the tarball URL specified in pip-requires.

Remove the 'deps = pep8==1.3.3' from tox.ini as it means all the other
deps get installed with easy_install which can't install oslo-config
from the URL.

Make tools/hacking.py include oslo in IMPORT_EXCEPTIONS like it already
does for paste. It turns out imp.find_module() doesn't correct handle
namespace packages.

Retain dummy cfg.py file until keystoneclient middleware has been
updated (I18c450174277c8e2d15ed93879da6cd92074c27a).

Change-Id: I4815aeb8a9341a31a250e920157f15ee15cfc5bc

nova/test.py

@@ -31,6 +31,7 @@ import uuid
 import eventlet
 import fixtures
 import mox
+from oslo.config import cfg
 import stubout
 import testtools
 
@@ -38,7 +39,6 @@ from nova import context
 from nova import db
 from nova.db import migration
 from nova.network import manager as network_manager
-from nova.openstack.common import cfg
 from nova.openstack.common.db.sqlalchemy import session
 from nova.openstack.common import log as logging
 from nova.openstack.common import timeutils