message: Remember to map the copy-out tensors in map ops
diff: #include <poplar/Graph.hpp>
  #include <poplar/Engine.hpp>
  +#include <popstd/ActivationMapping.hpp>
  namespace xla {
  namespace poplarplugin {
  @@ -139,6 +140,7 @@ CreateCallOp(poplar::Graph &graph,
  poplar::Tensor o = graph.addTensor(
  graph.getTensorElementType(v->outputs()[i]),
  v->outputs()[i].shape());
  + popstd::mapTensor(graph, o);
  seq.add(poplar::program::Copy(v->outputs()[i], o));
  TF_RETURN_IF_ERROR(AddOutputTensor(tensor_map, inst, i, o));
  }
  