plugin/file: less notify logging spam (#3212)

Say once that we've sent notifies, instead of for every upstream
primary.
Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/file/notify.go

@@ -53,10 +53,9 @@ func notify(zone string, to []string) error {
 		}
 		if err := notifyAddr(c, m, t); err != nil {
 			log.Error(err.Error())
-		} else {
-			log.Infof("Sent notify for zone %q to %q", zone, t)
 		}
 	}
+	log.Infof("Sent notifies for zone %q to %v", zone, to)
 	return nil
 }