Remove shortform of averaging in average tool

[Atticus1806]

I encountered this weird issue that this line would crash with RuntimeError: result type Float can't be cast to the desired output type Long when out_model_state[k] was of type int64.
Can be reproduced like:

import torch
x = torch.Tensor([1]).to(torch.int64)
x /= 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: result type Float can't be cast to the desired output type Long

Not doing the short form but instead x = x / 1 works.