cpu: skip percpu percent test if windows. Windows can only get one CPU info currently.

cpu/cpu_test.go

@@ -62,14 +62,16 @@ func TestCpuInfo(t *testing.T) {
 }
 
 func testCPUPercent(t *testing.T, percpu bool) {
+	numcpu := runtime.NumCPU()
+	if runtime.GOOS != "windows" {
 		v, err := CPUPercent(time.Millisecond, percpu)
 		if err != nil {
 			t.Errorf("error %v", err)
 		}
-	numcpu := runtime.NumCPU()
 		if (percpu && len(v) != numcpu) || (!percpu && len(v) != 1) {
 			t.Fatalf("wrong number of entries from CPUPercent: %v", v)
 		}
+	}
 	for i := 0; i < 100; i++ {
 		duration := time.Duration(10) * time.Microsecond
 		v, err := CPUPercent(duration, percpu)