godep seems to have a problem when dependencies have `internal`
packages. So removing `godep go build` and `godep go test` from the
build process in favor of just checking out the correct revisions using
`godep restore` into the regular GOPATH.
This basically means that we are not actually using anything within the
Godeps directory except Godeps.json. I should probably make a separate
go dependency management system that does this.
The test to see which version of `useradd` is installed uses 'bashisms'
that fail on Ubuntu due to the fact that `/bin/sh` is symlinked to Dash,
causing the telegraf account to be created without the `--system` option
ever being passed.
This change amends the syntax so that it's POSIX-compatible and more
portable as a result.