Bump stable/havana next version to 2013.2.3

Change-Id: Ia5b940faf01df6cae58df1f4b4f5e8fa2f3f078a
Merge "Bump stable/havana next version to 2013.2.3" into stable/havana
Merge branch 'stable/havana' of https://github.com/openstack/quantum into havana/stable