fix flatten infershape; test=develop

Author: danleifeng

python/paddle/fluid/tests/unittests/test_flatten2_op.py

@@ -70,7 +70,7 @@ def init_test_case(self):
         self.new_shape = (36, 16)
 
 
-class TestStaticFlattenPythonAPI(unittest.TestCase):
+class TestStaticFlattenInferShapePythonAPI(unittest.TestCase):
     def execute_api(self, x, axis=1):
         return fluid.layers.flatten(x, axis=axis)
 

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

@@ -201,7 +201,7 @@ def test_static_api(self):
         self.assertTrue((2, 3, 16) == fetch_out[0].shape)
 
 
-class TestStaticFlattenPythonAPI(unittest.TestCase):
+class TestStaticFlattenInferShapePythonAPI(unittest.TestCase):
     def execute_api(self, x, start_axis=0, stop_axis=-1):
         return paddle.flatten(x, start_axis, stop_axis)