Get rid of most references to GOPATH

hack/make-rules/test.sh

@@ -39,7 +39,6 @@ kube::test::find_dirs() {
         \( \
           -path './_artifacts/*' \
           -o -path './_output/*' \
-          -o -path './_gopath/*' \
           -o -path './cmd/kubeadm/test/*' \
           -o -path './contrib/podex/*' \
           -o -path './release/*' \