URL in Series of URL is triggered twice
I would like to have a switch that triggers the execution of requests in sequence. In my example, I want to say something over multiple Sonos speakers using the sonos-http-api. Following sequence scheme is used:

```json
[
    "<Request1>", 
    "delay(4000)",
    "<Request2>"
]
```

I am using the `"multipleUrlExecutionStrategy": "series"` and would expect that each request in the series is only executed once. However, when the switch is triggered, Request1 is executed twice, once immediately and once after the delay. Request2 is executed after the delay time, so that both requests are executed simultaneously after 4s. Am I misunderstanding the series with delays concept or is this a bug? 

**Version**
 - homebridge: v1.7.0
 - homebridge-http-switch: v0.5.36

**Actual Configuration**
```json
{
    "accessory": "HTTP-SWITCH",
    "name": "Say Something",
    "switchType": "stateless",
    "timeout": 8000,
    "debug": true,
    "multipleUrlExecutionStrategy": "series",
    "onUrl": [
        {
            "url": "http://localhost:5005/Room1/say/Hello%20in%20Room1"
        },
        "delay(4000)",
        {
            "url": "http://localhost:5005/Room2/say/Hello%20in%20Room2"
        }
    ]
}
```
