Also enable s3ng flags for the metadata storage

storage/pkg/flagset/storagemetadata.go

@@ -105,6 +105,7 @@ func StorageMetadata(cfg *config.Config) []cli.Flag {
 	f = append(f, DriverLocalWithConfig(cfg)...)
 	f = append(f, DriverOwnCloudWithConfig(cfg)...)
 	f = append(f, DriverOCISWithConfig(cfg)...)
+	f = append(f, DriverS3NGWithConfig(cfg)...)
 	return f
 
 }