fix the device inconsistency for import convert_sync_batchnorm (#38729)
Summary:
This fixes the device inconsistency reported in https://github.com/pytorch/pytorch/issues/37930
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38729
Differential Revision: D21671039
Pulled By: ngimel
fbshipit-source-id: 17fdb4eae2ddaf64560dd026fe39958536ab313f
