ensure metadata follow a specific folder

fix https://github.com/seaweedfs/seaweedfs/issues/5774

unmaintained/load_test/load_test_meta_tail/load_test_meta_tail.go

@@ -10,6 +10,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials/insecure"
 	"strconv"
+	"strings"
 	"time"
 )
 
@@ -79,12 +80,17 @@ func startGenerateMetadata() {
 
 func startSubscribeMetadata(eachEntryFunc func(event *filer_pb.SubscribeMetadataResponse) error) {
 
+	prefix := *dir
+	if !strings.HasSuffix(prefix, "/") {
+		prefix = prefix + "/"
+	}
+
 	metadataFollowOption := &pb.MetadataFollowOption{
 		ClientName:             "tail",
 		ClientId:               0,
 		ClientEpoch:            0,
 		SelfSignature:          0,
-		PathPrefix:             *dir,
+		PathPrefix:             prefix,
 		AdditionalPathPrefixes: nil,
 		DirectoriesToWatch:     nil,
 		StartTsNs:              0,