Direct statistics RPCs do not return error information on failure

Direct statistics RPCs do not provide any error information when it fails.

For example, get-queue-statistics RPC should fail if the specified queue does not exist.

POST /restconf/operations/opendaylight-direct-statistics:get-queue-statistics
Body:
{
"input":

{ "node": "/opendaylight-inventory:nodes/opendaylight-inventory:node[opendaylight-inventory:id=\"openflow:1\"]", "node-connector-id": "1", "queue-id": "12345" }

}

If the queue ID 12345 does not exist on the port "openflow:1:1", OF switch will return QUEUE_OP_FAILED/BAD_QUEUE error. But get-queue-statistics RPC returns an empty response.

HTTP/1.1 200 OK
Content-Type: application/yang.operation+json
Content-Length: 0
Server: Jetty(8.1.19.v20160209)