Fix for package versioning

Due to a limitation in the reprepo server in use by Docker.io, virtual packages (package=ver) is not supported.
This recipe no longer works as Docker has updated to version 0.6.5. The latest version can be referenced as lxc-docker, and doesn't appear to cause any compatibility issues, but for safety's sake I've referenced 0.6.4 that we've been using all along.