fix check backup is incremental path refs #23246

tests/test_backup.py

@@ -85,7 +85,7 @@ def check_backup_is_incremental(path):
 
     for d in dirs:
         num_folders = 0
-        if os.path.isdir(d):
+        if os.path.isdir(os.path.join(path, d)):
             media = glob.glob(os.path.join(path, d, "*/msinstance/media/resources/"))
             for m in media:
                 num_folders += len(os.listdir(m))