testing: shorten go test -short testing

This cuts the time for 'go test -short testing' from 0.9s to < 0.1s.

Change-Id: Ib8402f80239e1e96ea5221dfd5cd0db08170d85b
Reviewed-on: https://go-review.googlesource.com/c/go/+/177420
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/testing/benchmark_test.go

@@ -68,6 +68,9 @@ func TestResultString(t *testing.T) {
 }
 
 func TestRunParallel(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
 	testing.Benchmark(func(b *testing.B) {
 		procs := uint32(0)
 		iters := uint64(0)

src/testing/sub_test.go

@@ -756,6 +756,9 @@ func TestLogAfterComplete(t *T) {
 }
 
 func TestBenchmark(t *T) {
+	if Short() {
+		t.Skip("skipping in short mode")
+	}
 	res := Benchmark(func(b *B) {
 		for i := 0; i < 5; i++ {
 			b.Run("", func(b *B) {