Comment 4 for bug 1647719

Found one non-idempotency issue when re-running with
  - name: swift_0
    flavor: objectstorage
in the overcloud_nodes:

TASK [setup/overcloud : Attach additional blockdevices to overcloud objectstorage VMs] ***
...
failed: [virthost] (item=[{u'flavor': u'objectstorage', u'name': u'swift_0'}, u'vdd']) => {"changed": true, "cmd": ["virsh", "attach-disk", "--config", "swift_0", "/home/stack/.quickstart/pool/swift_0_vdd.img", "vdd"], "delta": "0:00:00.034526", "end": "2016-12-08 04:01:10.547250", "failed": true, "item": [{"flavor": "objectstorage", "name": "swift_0"}, "vdd"], "rc": 1, "start": "2016-12-08 04:01:10.512724", "stderr": "error: Failed to attach disk\nerror: Requested operation is not valid: target vdd already exists", "stdout": "", "stdout_lines": [], "warnings": []}