unitize name in optimizer; test=develop (#24008)

python/paddle/fluid/optimizer.py

@@ -68,16 +68,13 @@ class Optimizer(object):
                  grad_clip=None,
                  name=None):
         self._parameter_list = parameter_list
+        self._name = name
         if framework.in_dygraph_mode():
             if not isinstance(learning_rate, float) and \
                     not isinstance(learning_rate, LearningRateDecay):
                 raise TypeError(
                     "learning rate should be float or LearningRateDecay, got %s here"
                     % type(learning_rate))
-            if name is not None:
-                self._name = unique_name.generate(name)
-            else:
-                self._name = unique_name.generate(self.__class__.__name__)
             if self._parameter_list is None:
                 raise AttributeError(
                     "parameter_list argument given to the Optimizer should not be None in dygraph mode."
@@ -96,7 +93,6 @@ class Optimizer(object):
                 raise TypeError(
                     "learning rate should be float or Variable, got %s here" %
                     type(learning_rate))
-            self._name = name
 
         if grad_clip is not None:
             if not isinstance(grad_clip, GradientClipBase):