cinder tests fail.

To reproduce:

1. git clone git://github.com/openstack/cinder.git
2. cd cinder ; python setup.py sdist
3. cd cinder/dist
4. tar -zxvf cinder-xxxx.tar.gz
5 cd cinder-xxx
6. ./run_test.sh -N

You get tracebacks like the following:

----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/buildd/cinder-2013.1.a160.g0c52162/cinder/tests/test_test.py", line 33, in test_service_isolation
    self.start_service('volume')
  File "/tmp/buildd/cinder-2013.1.a160.g0c52162/cinder/test.py", line 184, in start_service
    svc.start()
  File "/tmp/buildd/cinder-2013.1.a160.g0c52162/cinder/service.py", line 340, in start
    version_string = version.version_string()
  File "/tmp/buildd/cinder-2013.1.a160.g0c52162/cinder/openstack/common/version.py", line 63, in version_string
    for part in self.release_string().split('.'):
AttributeError: 'NoneType' object has no attribute 'split'