Fix log silencing in tests

Tests were broken in Go 1.14.

devices/bmxx80/bmx280_test.go

@@ -6,6 +6,7 @@ package bmxx80
 
 import (
 	"errors"
+	"flag"
 	"io/ioutil"
 	"log"
 	"os"
@@ -610,10 +611,6 @@ func TestI2CSenseContinuous280_command_fail(t *testing.T) {
 }
 
 func TestI2CSenseContinuous280_sense_fail(t *testing.T) {
-	if !testing.Verbose() {
-		log.SetOutput(ioutil.Discard)
-		defer log.SetOutput(os.Stderr)
-	}
 	bus := i2ctest.Playback{
 		Ops: []i2ctest.IO{
 			// Chip ID detection.
@@ -1027,3 +1024,11 @@ type spiFail struct {
 func (s *spiFail) Connect(f physic.Frequency, mode spi.Mode, bits int) (spi.Conn, error) {
 	return nil, errors.New("failing")
 }
+
+func TestMain(m *testing.M) {
+	flag.Parse()
+	if !testing.Verbose() {
+		log.SetOutput(ioutil.Discard)
+	}
+	os.Exit(m.Run())
+}

devices/cap1xxx/cap1xxx_test.go

@@ -8,6 +8,7 @@ import (
 	"flag"
 	"io/ioutil"
 	"log"
+	"os"
 	"reflect"
 	"testing"
 	"time"
@@ -230,8 +231,12 @@ func setupPlaybackIO() []i2ctest.IO {
 
 func init() {
 	sleep = func(time.Duration) {}
+}
+
+func TestMain(m *testing.M) {
 	flag.Parse()
 	if !testing.Verbose() {
 		log.SetOutput(ioutil.Discard)
 	}
+	os.Exit(m.Run())
 }