Failed FileStation Upload API

Run:

```
@client = SYNOWebAPI::Client.new(URL)
@client.connect(
  username: USERNAME,
  password: PASSWORD,
  session_name: "FileStation"
)

@client["SYNO.FileStation.Upload"].request(method: "upload", version: 2, path: dest_path, filename: File.binread(src_path))

@client.disconnect
```

Result:

```
Faraday::ConnectionFailed: Broken pipe
```