make dev properly copies the binary into bin/ again.

make release still creates binaries for as many archs as possible.

Fixes #2407

This PR fixes our vet script and fixes all the missed vet changes.

It also fixes pointers being printed in `nomad stop <job>` and `nomad
node-status <node>`.

Saves a backup file using a gitignored extension.

The dev build is far simpler than the release build, so move it to its
own shell script. This simplifies the release build script slightly as
well at the cost of duplicating the version/tag logic.

Also don't even try to check for LXC if not running on Linux. I don't
think we want to try to support cross-compiling LXC from non-Linux
hosts.

We recently ran into an issue on a small percentage of nomad-clients
where the nomad-client was running successfully, but due to a race
condition, could not correctly bind to the docker socket. This caused
all of our nomad jobs to be allocated to a single nomad-client instead
of being spread evenly across our clients. The only way to discover this
was to run `nomad node-status <node>` and count each job allocation per
node.

This can lead to a fairly long debugging process if there are several
nomad-clients. Including the number of allocations for each node in the
`node-status` command would save a large amount of debug time.

```
jake@biscuits [12:08:41] [~]
-> % nomad node-status
ID        Datacenter  Name      Class   Drain  Status  Allocations
2b0aabc5  dc1         biscuits  <none>  false  ready   0
```

```
jake@biscuits [12:08:55] [~]
-> % nomad node-status
ID        Datacenter  Name      Class   Drain  Status  Allocations
2b0aabc5  dc1         biscuits  <none>  false  ready   1
```

- Introduces a travis target in Makefile to update docker and
  install rkt

Lifted from https://github.com/fsouza/go-dockerclient

BSD Make uses `$.CURDIR` instead of `$CURDIR`. BSD and GNU share `$PWD`
though, so it works as a drop in replacement.

Also update scripts in `scripts/` to call `/usr/bin/env` in the shebang,
as BSD places `bash` at `/usr/local/bin/bash` instead of `/bin/bash`

These two tools are used in the "cov" Makefile target, but installing
these were not automated. This PR removes the ambiguity where a
developer tries to do a `make cov` and finds that the tools are not
installed.