ref(store): reduce image size

```console
deis/store-gateway             resize         dcab069cc0cf        14 hours ago        359.2 MB
deis/store-monitor             resize         8cf691e859c3        14 hours ago        268.2 MB
deis/store-daemon              resize         23f16528ac03        14 hours ago        268.2 MB
deis/store-base                resize         ef1677bae515        14 hours ago        268.2 MB
```
I'm pretty sure we need to run `apt-get update` again here so the repos are refreshed with the Ceph mirrors we just added on the previous lines.