Summary:
Changelog: [internal]
`LazyShadowTreeRevisionConsistencyManager` wasn't correctly updating the locked revision, because `emplace` is a no-op if there's already a value for the key in the `unordered_map`.
This fixes the issue and adds tests that actually showed it.
Reviewed By: sammy-SC
Differential Revision: D56761941
fbshipit-source-id: 340e9195b14460a591c48186bd365688c74ade04