Summary:
Two things
- Use thenValue instead of then in one specific occurrence as later one has been deprecated
- Build googletest on `release-1.8.1` as it is the one that compiles with c++11

Reviewed By: cenzhao

Differential Revision: D10178139

fbshipit-source-id: 069578716e5e55ef0a25ea87e9ef5ceded1ff9d6