Version bump for docker to 0.8.1

As @tianon mentioned in #26488, the Homebrew-specific patches were included upstream in Docker 0.8.1.

### Checksums
I've also removed the sha1 that was in there instead of updating it because I couldn't find what it referred to when using the GitDownloadStrategy. It seems to be ignored.

### Bottles
I've removed the bottle references because it looks like that's what other people are doing (eg a0197c023d87ab13a26dbab742bcb4c4cfce9383). It seems BrewTestBot adds them back in.