Prevent the entire Homebridge from being blocked if PiHole is offline
If Pihole is not available, Homebridge and all other devices are also unavailable.
Please implement an availability check of the PiHole server instead of blocking the entire Homebridge.

For more details on how a single accessory blocks the entire Homebridge, see [homebridge/homebridge#948](https://github.com/homebridge/homebridge/issues/948).