build: Rework Vagrant for multiple operating systems; add FreeBSD support

Expand TLS upgrade guide

This commit reworks the Vagrantfile for Nomad in order to support
straightforward testing on more than one operating system, whilst
retaining the ability to stand up a test cluster running Ubuntu.

The following changes are made:

- Scripts have been extracted from the Vagrantfile into their own shell
  script files, in order that editors lint them.

- All scripts have been edited to lint with no warnings or errors for
  their respective shells.

- Scripts are named according to the operating system and privilege
  level which they run. We prefer to run a whole shell script as root
  versus prefixing (essentially) every command with `sudo` or an
  equivalent.

- The Linux development box has been separated from the test cluster,
  removing some of the more gnarly (and less portable) logic. The Linux
  development box is still primary and autostarts.

- A FreeBSD target has been added. The base box works for both
  Virtualbox and VMWare Fusion.

- A target...

The old wording made it sound like verify_https_client=true broke *all*
https health checks.

Current plan for the future still requires two server restarts.

client: Guard against "NaN" values from floats

This commit protects against finding `0.NaN` tokens in JSON streams
because of infinity representation on serialization.

deps: Update golang.org/x/sys/{unix,windows}

Sync namespace changes

- Non-trivial clusters risk rescheduling many if not all of their jobs
  if they don't adjust their heartbeat configs.
- Still needs links

Tagged metrics API

docs fixup

Vendor cli to get exit code 127 on unknown command

Add testing around nomad job deployments command

WatchCtx propogates context error

[cli] Fix panic while running latest deployment command witch -latest flag

move metrics to telemetry; copy to client config

better api example, add telemetry documentation

prevent against flaky test due to timing/initialization issues

Always purge stopped containers

Fix repo name passed to docker credential helpers

Update go-getter