SystemEventLogs: Able to create event with node parameter specified explicitly

Build: 7.1.0-1635

Create an event by specifying the "node" parameter explicitly in the event dictionary.

    {

      "severity": "info",

      "description": "test_invalid_values",

      "uuid": "90048a2a-75ca-4557-a618-6064169eaccc",

      "node": "1.1.1.1",

      "component": "ns_server",

      "event_id": 0,

      "timestamp": "2021-11-04T15:33:32.875Z"

    }

'node' value specified should either be ignored by the ns_server and populated with the correct node details (or) event creation should fail with node value explicitly given.