backport tf2bc changes from barracuda-release (#3341)

ml-agents/mlagents/trainers/tensorflow_to_barracuda.py

@@ -592,9 +592,12 @@ def get_attr(node, attr_name, default=None):
     val = node.attr[attr_name]
 
     if val.HasField("list"):
-        return val.list.i
         # NOTE: can't find way to identify type of list BUT it is almost always list(int)
         # except list(float) in FractionalAvg/MaxPool
+        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"):
@@ -618,6 +621,10 @@ def get_epsilon(layer):
 
 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):
@@ -753,7 +760,7 @@ def axis_to_barracuda(axis, input_rank):
     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: