bundlerepository: test self.tempfile field, not tempfile module

This error was introduced in 680fe77ab5b8.

mercurial/bundlerepo.py

@@ -252,8 +252,8 b' class bundlerepository(localrepo.localre'
 
     def __del__(self):
         del self.bundle
-        if tempfile is not None:
-            os.unlink(tempfile)
+        if self.tempfile is not None:
+            os.unlink(self.tempfile)
         if self._tempparent:
             shutil.rmtree(self._tempparent, True)