test: remove errgroup to take advantage of vet
test: remove errgroup to take advantage of vet

go vet would have prevented the bug fixed in
6362e32161295fa959ebe46b93cea0ea1a9bdd72 but our use of errgroup
prevented that.

Rip out errgroup to take advantage of vet, and remove download limiting
now that we're downloading far fewer binaries overall.

hashicorp/nomad,burdandrei/nomad,hashicorp/nomad,dvusboy/nomad,dvusboy/nomad,dvusboy/nomad,dvusboy/nomad,burdandrei/nomad,burdandrei/nomad,hashicorp/nomad,hashicorp/nomad,burdandrei/nomad,burdandrei/nomad,hashicorp/nomad,hashicorp/nomad,dvusboy/nomad,dvusboy/nomad,burdandrei/nomad,dvusboy/nomad,burdandrei/nomad