chore: set default value of retry_interval to 1

the prior default value 0 would make hysteria retry very fast
(2000 times / sec) when network is not ready (no default route).

user can still set it to 0 explicitly for a "flood retry" mode.

app/cmd/client.go

@@ -152,11 +152,15 @@ func client(config *clientConfig) {
 		if err != nil {
 			logrus.WithField("error", err).Error("Failed to initialize client")
 			if try <= config.Retry || config.Retry < 0 {
+				retryInterval := 1
+				if config.RetryInterval != nil {
+					retryInterval = *config.RetryInterval
+				}
 				logrus.WithFields(logrus.Fields{
 					"retry":    try,
-					"interval": config.RetryInterval,
+					"interval": retryInterval,
 				}).Info("Retrying...")
-				time.Sleep(time.Duration(config.RetryInterval) * time.Second)
+				time.Sleep(time.Duration(retryInterval) * time.Second)
 			} else {
 				logrus.Fatal("Out of retries, exiting...")
 			}

app/cmd/config.go

@@ -167,7 +167,7 @@ type clientConfig struct {
 	DownMbps int    `json:"down_mbps"`
 	// Optional below
 	Retry            int  `json:"retry"`
-	RetryInterval    int  `json:"retry_interval"`
+	RetryInterval    *int `json:"retry_interval"`
 	QuitOnDisconnect bool `json:"quit_on_disconnect"`
 	HandshakeTimeout int  `json:"handshake_timeout"`
 	IdleTimeout      int  `json:"idle_timeout"`