[Bug] Shelly Bulb disconnects if in 'White' mode
**Describe the bug**
Whenever the bulb is in 'White' mode and you then turn it either on or off via Homebridge or HomeKit it disconnects (`Error: Timeout of 10000ms exceeded`). After some time it comes back online but is on RGB mode. 

If the device is in RGB mode however everything works fine. It's probably an issue with how the plugin handles the 'White' mode.

**Log output**
```
[Shelly] Failed to set light
Error: Timeout of 10000ms exceeded (device SHCB-1 XXX, at 192.XXX)
```

**Environment:**
 - Shelly device(s): Shelly Duo - RGBW
 - Plugin version: 0.19.1
 - Device running homebridge: Docker
 
 
![image](https://user-images.githubusercontent.com/100965650/169305125-44cc94dc-a918-48c8-b3eb-7898696030c5.png)
