backport tf2bc changes from barracuda-release (#3341)

ml-agents/mlagents/trainers/tensorflow_to_barracuda.py

     val = node.attr[attr_name]
 
     if val.HasField("list"):
-        return val.list.i
+        if len(val.list.shape) > 0:
+            return val.list.shape
+        else:
+            return val.list.i
     if val.HasField("b"):
         return val.b
     if val.HasField("i"):
 
 def get_layer_rank(layer):
     shape = get_attr(layer, "shape")
+    if not shape:
+        outputShapes = get_attr(layer, "_output_shapes")
+        if outputShapes:
+            shape = outputShapes[0]
     if not shape:
         return None
     if isinstance(shape, list):
     W = 2
     C = 3
     if axis < 0:
-        axis = input_rank - axis
+        axis = input_rank + axis
     assert axis >= 0
     assert axis < input_rank
     if input_rank == 4: