Toolbox wedged after failed download

I ran `toolbox` on my machine before DNS had been configured.
```
$ toolbox
Pulling repository fedora
2014/08/18 21:18:52 Get https://index.docker.io/v1/repositories/fedora/images: dial tcp: lookup index.docker.io: connection refused
Unable to find image 'fedora:latest' locally
Pulling repository fedora
2014/08/18 21:18:52 Get https://index.docker.io/v1/repositories/fedora/images: dial tcp: lookup index.docker.io: connection refused
2014/08/18 21:18:52 Error: No such container: core-fedora-latest
tar: This does not look like a tar archive
tar: Exiting with failure status due to previous errors
Error response from daemon: No such container: core-fedora-latest
2014/08/18 21:18:52 Error: failed to remove one or more containers
touch: cannot touch '/var/lib/toolbox/core-fedora-latest/etc/os-release': No such file or directory
Directory /var/lib/toolbox/core-fedora-latest lacks the binary to execute or doesn't look like a binary tree. Refusing.
```
After this initial failure, toolbox was permanently stuck.
```
$ toolbox
unknown
Directory /var/lib/toolbox/core-fedora-latest lacks the binary to execute or doesn't look like a binary tree. Refusing.
```
Removing `/var/lib/toolbox/core-fedora-latest/` fixes the issue.