In-place layer followed by a viewing layer crashes on backprop

[tbennun]

If a layer is set to be in-place, and it is followed by a viewing layer (identity, reshape, etc.), and keep error signals is off, a crash happens in the deep-copy of the tensors during backprop. For now, we will have a very specific check that disables the in-placeness in this case, but we should remove that after the update.

@ndryden @benson31 Pinging you to fix this after new tensors are merged.