test=release/1.4 fix model_stat import bug

Author: AIFollowers

python/paddle/fluid/contrib/__init__.py

@@ -32,6 +32,8 @@
 from .utils import *
 from . import extend_optimizer
 from .extend_optimizer import *
+from . import model_stat
+from .model_stat import *
 
 __all__ = []
 __all__ += decoder.__all__