fixing problem with existing Singleton Caching (apache#15868)

Author: access2rohit

python/mxnet/runtime.py

@@ -77,11 +77,9 @@ class Features(collections.OrderedDict):
     def __new__(cls):
         if cls.instance is None:
             cls.instance = super(Features, cls).__new__(cls)
+            super(Features, cls.instance).__init__([(f.name, f) for f in feature_list()])
         return cls.instance
 
-    def __init__(self):
-        super(Features, self).__init__([(f.name, f) for f in feature_list()])
-
     def __repr__(self):
         return str(list(self.values()))