unix: fix SysctlUint64 on 32bit machines

TestSysctlUint64 was using vm.max_kernel_address which is only 64bit
on 64bit machines or 32bit machines with PAE. Switch to using
security.mac.labeled which is a SYSCTL_UQUAD so 64bit on all platforms.

Also:
* Correct typo in test name.

Fixes golang/go#15186

Change-Id: I88b5b6ee6a04dec0730bca1e1f0e282f3c18d20d
Reviewed-on: https://go-review.googlesource.com/36058Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

unix/syscall_freebsd_test.go

@@ -7,18 +7,14 @@
 package unix_test
 
 import (
-	"os"
 	"testing"
 
 	"golang.org/x/sys/unix"
 )
 
-func TestSysctUint64(t *testing.T) {
-	_, err := unix.SysctlUint64("vm.max_kernel_address")
+func TestSysctlUint64(t *testing.T) {
+	_, err := unix.SysctlUint64("security.mac.labeled")
 	if err != nil {
-		if os.Getenv("GO_BUILDER_NAME") == "freebsd-386-gce101" {
-			t.Skipf("Ignoring known failing test (golang.org/issue/15186). Failed with: %v", err)
-		}
 		t.Fatal(err)
 	}
 }