Ensure KeepaliveTimerTest.cpp is built properly.
Ensure KeepaliveTimerTest.cpp is built properly.

Summary: KeepaliveTimerTest.cpp build broke after https://github.com/ReactiveSocket/reactivesocket-cpp/commit/3b39c48e5928f3767975c04693d4af58ceb0f777

Reviewed By: lehecka

Differential Revision: D4694299

fbshipit-source-id: c09b820d613b3cc2a28d76d934d41ccf9b93a6c8

alexmalyshev/rsocket-cpp,phoad/rsocket-cpp,rsocket/rsocket-cpp,vjn/reactivesocket-cpp,phoad/rsocket-cpp,vjn/reactivesocket-cpp,vjn/rsocket-cpp,ReactiveSocket/reactivesocket-cpp,ReactiveSocket/reactivesocket-cpp,alexmalyshev/rsocket-cpp,alexmalyshev/rsocket-cpp,rsocket/rsocket-cpp,rsocket/rsocket-cpp,alexmalyshev/rsocket-cpp,vjn/rsocket-cpp,phoad/rsocket-cpp,vjn/rsocket-cpp,phoad/rsocket-cpp,vjn/reactivesocket-cpp,rsocket/rsocket-cpp,ReactiveSocket/reactivesocket-cpp,phoad/rsocket-cpp