Allow for disabling the automatic save on shutdown.

This is bad for mesh-tensorflow, where the variables to be saved haven't gotten
updated since the previous checkpoint was written.

PiperOrigin-RevId: 357126243

Author: nshazeer

mesh_tensorflow/transformer/utils.py

@@ -1697,7 +1697,8 @@ def get_estimator(model_type, vocabulary, mesh_shape,
       tpu_config=my_tpu_config,
       session_config=session_config,
       save_checkpoints_steps=save_checkpoints_steps,
-      save_checkpoints_secs=None)
+      save_checkpoints_secs=None,
+      save_checkpoint_on_shutdown=False)
 
   transformer_model = build_model(
       model_type=model_type,