Return `extravars` & `credentials` as a JSON object not a JSON string

[dsha256]

Currently extravars & credentials are returned as a JSON string. Returning them as JSON objects would be great.

Currently:

"extravars": "{\"name\":\"vm1\",\"region\":\"myregion\",\"opco\":\"myopco\"}"

After:

{
  "name": "vm1",
  "opco": "myopco",
  "region": "myregion"
}