Always parse body if inputFormat is set

This was originally written as it was to avoid a BC issue, but it's possible to miss JSON input with more complex JSON structures.

```json
{
    "var": {
        "test": false,
        "foo": "bar", 
        "baz": 0, 
        "bing": []
    },
}
```

This will result in the broken behavior.

If you are sending `Content-Type: application/json`, `Content-Type: application/xml` or similar, then you're probably wanting to send JSON or XML — I don't think this will be an issue.