Presence: Not all devices are checked
Hi there,

I tried out the presence feature (my main feature in this plugin), but sadly it does not work very well. It seems like only the first and the last device is updated correctly.

E.g.:
```javascript
    "presence": {
        "anyoneSensor": true,
        "delay": 30,
        "type": "motion",
        "devices": {
          "Handy 1": "MAC", // connected -> plugin shows connected -> correct
          "Handy 2": "MAC", // connected -> plugin shows DISCONNECTED -> BUG
          "Handy 3": "MAC", // disconnected-> plugin shows disconnected -> correct
          "Handy 4": "MAC", // connected -> plugin shows DISCONNECTED -> BUG
          "Handy 5": "MAC"  // disconnected-> plugin shows disconnected -> correct
        }
      }
```

On startup I get the message `[FritzBox] [INFO] Welcome at home Handy 1` and a few lines later it prints `[FritzBox] [WARN] Handy 5: Switching to no presence`. 
The status is correct for these two ones, but your plugin does not detect (or even check) the other devices (Handy 2 and 4 were connected to the network as well).

Edit: Works fine on version 2.6.4, just not with the latest one.

Best regards