Fix umount retry

lmm/cli.py

@@ -1,5 +1,6 @@
 import os
 from typing import Optional
+import time
 
 from lmm.config import LMMConfig
 from lmm.const import LMM_GAMES_PATH

lmm/overlayfs.py

@@ -136,7 +136,7 @@ class OverlayFSMount:
                     print(f"Failed to clean temporary directory {self.workdir.name}")
 
             self._mounted = False
-            return True
+        return True
 
     def __del__(self):
         self.unmount()