chore(*): bump CoreOS to 509.1.0 for Docker vulnerability

This PR updates CoreOS to include
[Docker 1.3.2](https://github.com/docker/docker/blob/master/CHANGELOG.md#132-2014-11-20)
which includes [important security fixes](https://groups.google.com/forum/#!msg/docker-user/IrjXTHA6jJc/ZToMGL2yG_AJ).

In addition to upgrading to Docker 1.3.2, we are addressing the
secure-by-default registry settings in #2578 (these changes were
introduced in Docker 1.3.1).

Note that DigitalOcean and Rackspace do not yet have CoreOS 509.1.0.