Replace SwitchToDevice(0) with SwitchToDevice() (#15126)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15126
I want to make people stop manufacturing StreamId from thin air,
and a first step is to make people use the default stream.
Reviewed By: dzhulgakov
Differential Revision: D13432922
fbshipit-source-id: 9f0d8d70646c50d979bde5ba3c3addeebac48a3d
