REST Data Messages metric has stale value type

[lorthirk]

Describe the bug
The messages returned by the Data Messages REST does not seem to update the metric value type if this has changed.

To Reproduce
Steps to reproduce the behavior:

1. Send a data message
2. Use REST API to retrieve the message back
3. Observe the difference in metric value

Actual behaviour
The value type (string) of themetric_1 metric returned by the Data Messages REST does not match the type shown by Kapua Console (long) or the one returned by the Data Metric REST (long). Long is the type currently published by the device.

Expected behaviour
The value type of the metric_1 metric in the most recent messages returned by the Data Messages REST should be long.

Version of Kapua
1.1.0

Type of deployment
[ ] Local Vagrant deployment
[x] Docker
[ ] Openshift (in its variants)
[ ] Others

Main component affected
[ ] Console (in case of console please report info on which browser you encountered the problem)
[x] REST API
[ ] Message Broker
[ ] - Others

Additional context

REST Data Message

{
  "type": "jsonDatastoreMessage",
  "channel": {
    "semanticParts": ["channel-part-1"]
  },
  "clientId": "45F4DD37EA82",
  "deviceId": "R9Yezfu9i6g",
  "payload": {
    "body": "U2FtcGxlIGJvZHkgc3RyaW5n",
    "metrics": [
      {
        "valueType": "string",
        "value": "1104",
        "name": "metric_1"
      }
    ]
  },
  "receivedOn": "2019-06-14T10:13:07.526Z",
  "scopeId": "Wm9r0bh3bv8",
  "datastoreId": "15d256e3-618f-4260-bd49-1e80a7405ccd",
  "timestamp": "2019-06-14T10:13:07.537Z"
}