Dockerfile.k8s still has bzr

[neil-pozetroninc]

As part of our effort to provide a community developed Helm chart we currently build the k8s Docker image automatically.

Since bzr is no longer available in Alpine Linux as of 3.12 (alpinelinux/docker-alpine#87) these no longer build. The fix is the same as was done for the standalone Dockerfile.

Thanks for the awesome software and we hope that the Helm chart can help someone!

[tylertreat]

Awesome to see the Helm chart, wasn't even aware! Will get the k8s Dockerfile fixed up.