This commit rewrites the Vagrantfile for Packer in a similar manner to
the work done for Nomad (hashicorp/nomad#3175) in order to make
cross-platform development easier. It also adds support for a FreeBSD
base box.
Provisioning scripts are separated out in order that they can be
correctly linted. Each script is prefixed `vagrant`, then the operating
system, then whether or not it expects to be run in a privileged shell.
Finally, dependencies have been bumped - Go 1.6 is switched out for the
latest (1.9.2).
4fc0a1ea0a