Silence net.OpErrors dealing with accept.

This code is borrowed from:
https://github.com/stretchr/graceful/blob/6e11439113e0d071338d6be3f10d7772817faf59/graceful.go#L52-L58

http/http.go

@@ -128,7 +128,9 @@ func Serve(cfg *config.Config, tkr *tracker.Tracker) {
 	}
 
 	if err := grace.ListenAndServe(); err != nil {
-		glog.Errorf("Failed to start server: %s", err.Error())
+		if opErr, ok := err.(*net.OpError); !ok || (ok && opErr.Op != "accept") {
+			glog.Errorf("Failed to gracefully run HTTP server: %s", err.Error())
+		}
 	}
 
 	if err := srv.tracker.Close(); err != nil {