Display NSO diff errors to admin users

[jonstout]

Every once in a while a device will be out of sync with nso when performing its diff. We should ensure that these errors are displayed to the user to eliminate any confusion.

Example:

{
  "ietf-restconf:errors": {
    "error": [
      {
        "error-type": "application",
        "error-tag": "malformed-message",
        "error-path": "/tailf-ncs:services/oess-l3connection:oess-l3connection[connection_id='0000']",
        "error-message": "Network Element Driver: device example.name: out of sync"
      }
    ]
  }
}