The START payload can only contain one volume

[markdryan]

Right now the we can only specify one ceph volume to be attached to an instance at start time, which seems a little restrictive as you can Attach as many volumes as you like at runtime. It also means that if you boot from volume you cannot attach a second ceph data volume to that instance at creation time.

We should be able to do something like

start:
  ... 
  storage:
    -  id: 67d86208-000-4465-9018-fe14087d415f
        boot: true
    -  id: 67d86208-111-4465-9018-fe14087d415f
        boot: false

[tpepper]

In order to support the OpenStack block-device-mapping-v2 as per issues #387 and #373 I need this to be a list of StorageResources objects, not just one StorageResources object.