dnstap.TapperFromContext always returns nil (#2018)

Automatically submitted.

plugin/dnstap/context_test.go

@@ -0,0 +1,15 @@
+package dnstap
+
+import (
+	"context"
+	"testing"
+)
+
+func TestDnstapContext(t *testing.T) {
+	ctx := tapContext{context.TODO(), Dnstap{}}
+	tapper := TapperFromContext(ctx)
+
+	if tapper == nil {
+		t.Fatal("Can't get tapper")
+	}
+}