runtime/race: also unmap memory if TestNonGoMemory fails

Change-Id: I7ea150e4896fc9b2e3a6dbdd9a1c2b651e74b844
Reviewed-on: https://go-review.googlesource.com/c/go/+/428778
Auto-Submit: Tobias Klauser <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Run-TryBot: Tobias Klauser <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: tklauser

src/runtime/race/race_unix_test.go

@@ -19,11 +19,11 @@ func TestNonGoMemory(t *testing.T) {
 	if err != nil {
 		t.Fatalf("failed to mmap memory: %v", err)
 	}
+	defer syscall.Munmap(data)
 	p := (*uint32)(unsafe.Pointer(&data[0]))
 	atomic.AddUint32(p, 1)
 	(*p)++
 	if *p != 2 {
 		t.Fatalf("data[0] = %v, expect 2", *p)
 	}
-	syscall.Munmap(data)
 }