Comment 11 for bug 1687712

David, for your point '2' above (comment 9), there was never any support for cmd being an array. That is something that could be added, but is not a regression.

See the previous code at
 https://git.launchpad.net/cloud-init/tree/cloudinit/config/cc_disk_setup.py?id=99faf3ece1badc566e7e75e769ff374250196197#n912

And the changes made at
  https://git.launchpad.net/cloud-init/commit/?id=4f0f171c29bb9abb5cbb6f9adbe68015089aeed9