The JSON payload is not remembered when invoking Dapr application again

[v-ruizh]

OS: Win10
Build Version: 20200827.4

Repro Steps:

1. Open a webapi project in VS Code.
2. F1 -> Dapr: Scaffold Dapr Tasks -> .NET Core Launch (web) -> Enter a Dapr ID 'app' for the application -> Enter the port '5000'.
3. Open the "Controllers/WeatherForecastController.cs" file.
4. Add the following within the class definition:

[HttpPost]
public ActionResult Post([FromBody] object body)
{
  return new JsonResult(body);
}

5. Switch to the debug tab and change the configuration to '.NET Core Launch (web) with Dapr', then F5.
6. F1 -> Dapr: Invoke (POST) Application Method -> Enter "WeatherForecast" as the application method -> Enter "{ "number": 42 }" as the JSON payload.
7. F1 -> Dapr: Invoke (POST) Application Method again -> Check the default JSON payload.

Expect:
The default JSON payload is remembered with "{ "number": 42 }".

Actual:
The default JSON payload is 'WeatherForecast', the JSON payload is not remembered.

More Info:
This issue does not reproduce on the previous released extension build.

[philliphoff]

This is the same symptom as #109, now fixed.