File_provider.push always pushes shmem
Summary:
This diff is part of a stack to make the provider.push_local_stack calls uniform. See
D20832355 for the fruits of this labor. Uniform means:
1. they all have an identical name
2. this name indicates that they always operate upon sharedmem
3. they don't do anything other than sharedmem
4. they don't take a context
5. they don't switch upon ctx.backend nor Provider_backend.get. Instead they assume that the caller has done the switch.
Reviewed By: arxanas
Differential Revision:
D20834233
fbshipit-source-id:
62482bbec307a491ec32e9e199fe30018c76de00