Pin Chef at 11.16.4

Chef client 12.0 dies horribly when we try using the cstruct gem.
Pin it at the last 11.x release for now.
Merge pull request #350 from VictorLowther/pin-chef-at-11.6

Pin Chef at 11.16.4
docker-admin is now a centos 7 container

The admin node has full functionality, but no care has been
taken to preserve backwards compatibility with a centos 6 based
admin node.

Part of that change was ditching using Apache for the provisioner
webserver in favor of a tiny static webserver in Go.
Switch from chef-server to goiardi, and refactor bootstrap recipes to split things out a bit
Build openwsman from source as part of bootstrap
Switch to using grub2 for PXE and UEFI netbooting