net/http: fix nits found by go tool vet

LGTM=ruiu
R=golang-codereviews, ruiu
CC=golang-codereviews
https://golang.org/cl/91480043

src/pkg/net/http/serve_test.go

@@ -2144,7 +2144,7 @@ func TestCodesPreventingContentTypeAndBody(t *testing.T) {
 			got := ht.rawResponse(req)
 			wantStatus := fmt.Sprintf("%d %s", code, StatusText(code))
 			if !strings.Contains(got, wantStatus) {
-				t.Errorf("Code %d: Wanted %q Modified for %q: %s", code, req, got)
+				t.Errorf("Code %d: Wanted %q Modified for %q: %s", code, wantStatus, req, got)
 			} else if strings.Contains(got, "Content-Length") {
 				t.Errorf("Code %d: Got a Content-Length from %q: %s", code, req, got)
 			} else if strings.Contains(got, "stuff") {

src/pkg/net/http/transport_test.go

@@ -2081,7 +2081,7 @@ func TestTransportClosesBodyOnError(t *testing.T) {
 		defer res.Body.Close()
 	}
 	if err == nil || !strings.Contains(err.Error(), fakeErr.Error()) {
-		t.Fatalf("Do error = %v; want something containing %q", fakeErr.Error())
+		t.Fatalf("Do error = %v; want something containing %q", err, fakeErr.Error())
 	}
 	select {
 	case err := <-readBody: