Adding support for Pi-hole running inside a Docker container

[IarwainBen-adar]

Made a small change to pihole-cloudsync in order to support cases where Pi-hole is running inside a Docker container (see: https://github.com/pi-hole/docker-pi-hole). Sorry about the tabs/spaces change, I know that's not exactly being a good citizen, but the meat of the Docker-support change should be pretty easy to merge in as (or if) you see fit.

[stevejenkins]

Would you mind taking a peak at v5 and see how the docker changes could be rolled in? Thanks!