chore(contrib/*): update CoreOS to 317.0.0

NOTE: We are waiting on Rackspace builds for CoreOS 317.0.0 before merging this.

The update to `fleetctl` 0.3.2 required some changes to `coreos.py` and our `Makefile`, so this is more than a normal CoreOS update for Deis. Some changes to systemd units and the Makefile were also inspired by integration testing.

TESTING: not yet. :smiley_cat: