fix fleet amp get_loss_scaling (#33935)

python/paddle/distributed/fleet/meta_optimizers/amp_optimizer.py

@@ -124,3 +124,6 @@ class AMPOptimizer(MetaOptimizerBase):
                  use_fp16_test=False):
         return self.wrapped_opt.amp_init(place, scope, test_program,
                                          use_fp16_test)
+
+    def get_loss_scaling(self):
+        return self.wrapped_opt.get_loss_scaling()

python/paddle/fluid/tests/unittests/test_fleet_amp_init.py

@@ -117,6 +117,7 @@ class TestFleetAMPInit(unittest.TestCase):
             optimizer.minimize(cost)
 
         print(fleet._get_applied_meta_list())
+        loss_scale = optimizer.get_loss_scaling()
 
         place = paddle.CUDAPlace(0)