chore(coreos): upgrade to 379.3.0 and Docker 1.1.1

This also bumps Docker to 1.1.1

Depends on https://github.com/deis/base/pull/8, as etcd is now 0.4.5 in these images. 

NOTE: @robszumski said we won't get updated Rackspace images until the 23rd at the earliest, according to Rackspace... :(

TESTING: Choose a provisioner and deploy Deis like normal. If not on Vagrant, make sure you export `DEIS_HOSTS` so the Makefile can build builder remotely. Then, rebuild and restart the builder:
```console
$ fleetctl stop deis-builder
$ make -C builder build
$ fleetctl start deis-builder
```

closes #1270
why is it xvda now?