Upgraded openstack.common to latest.

NOTE! Due to the introduction in os.common of an oslo-config dependency, to run with tox you need to get oslo-config into tox's venvs. I did this with:

(clone oslo-config to /opt/stack/oslo-config)
cd /opt/stack/oslo-config
../qonos/.tox/py26/bin/python ./setup.py install
../qonos/.tox/py27/bin/python ./setup.py install

There doesn't seem to be a good automatic way of getting oslo-config since it isn't in pypi nor managed as part of the os.common update process.