Don't end on inplace operators in einsum (#22111)
Summary:
Returning the result of an inplace `squeeze_` in `einsum` (which itself is traced) interacts badly with `autograd.Function`.
I must admit that I'm not 100% certain whether it should be necessary to change this, but I consider this a good change overall.
Fixes: https://github.com/pytorch/pytorch/issues/22072
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22111
Differential Revision: D15974990
Pulled By: soumith
fbshipit-source-id: 477e7f23833f02999085f665c175d062e7d32acd
