Run 'lint-install', address lint issues raised

[tstromberg]

See tinkerbell/lint-install#9

This adds new makefile rules: lint and fix, and addresses the following lint issues raised:

test/_kind/kind_test.go:124: File is not `gofumpt`-ed (gofumpt)

test/_kind/kind_test.go:125: File is not `gofmt`-ed with `-s` (gofmt)

test/_kind/kind_test.go:155:24: response body must be closed (bodyclose)
		resp, err := http.Get("http://localhost:42114/healthz")
		                     ^
test/_kind/kind_test.go:251:23: unused-parameter: parameter 'ctx' seems to be unused, consider removing or renaming it as _ (revive)
func registerHardware(ctx context.Context) error {
                      ^
test/_vagrant/vagrant_test.go:59:24: response body must be closed (bodyclose)
		resp, err := http.Get("http://localhost:42114/healthz")
		                     ^
test/_vagrant/vagrant_test.go:165:23: unused-parameter: parameter 'ctx' seems to be unused, consider removing or renaming it as _ (revive)
func registerHardware(ctx context.Context) error {
                      ^