plugin/dnstap: don't spam Travis + valid dnstap payload (#1121)

* don't spam Travis + valid dnstap payload

* log instead of fmt

* Revert "log instead of fmt"

This reverts commit 88f09c3939.

* log the right way

* log the final way

* minor enhancements

plugin/dnstap/dnstapio/io_test.go

@@ -2,6 +2,8 @@ package dnstapio
 
 import (
 	"bytes"
+	"io/ioutil"
+	"log"
 	"sync"
 	"testing"
 	"time"
@@ -9,6 +11,10 @@ import (
 	tap "github.com/dnstap/golang-dnstap"
 )
 
+func init() {
+	log.SetOutput(ioutil.Discard)
+}
+
 type buf struct {
 	*bytes.Buffer
 	cost time.Duration
@@ -38,7 +44,8 @@ func TestRace(t *testing.T) {
 					return
 				default:
 					time.Sleep(50 * time.Millisecond)
-					dio.Dnstap(tap.Dnstap{})
+					t := tap.Dnstap_MESSAGE
+					dio.Dnstap(tap.Dnstap{Type: &t})
 				}
 			}
 		}()