Materialize a non-default device for C2 legacy storage. (#18605)
Summary:
It's not intended that Storages have 'default' CUDA devices, but this is allowable via the Storage::create_legacy codepath.
This also messages with device_caching, because the initial cache is obtained from the Storage, which may have a 'default' device.
Instead, we materialize a device by allocating 0 bytes via the allocator.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18605
Differential Revision: D14680620
Pulled By: gchanan
fbshipit-source-id: 6d43383d836e90beaf12bfe37c3f0506843f5432
