Add ThriftClientTest future sync test case
Add ThriftClientTest future sync test case

Summary:
This change adds some test cases involving an synchronous use
of a futures based api, as suggested matching a specific use case.

Reviewed By: mnv104

Differential Revision: D14840464

fbshipit-source-id: cf4e327d0a09ad2516e70788d8087ec244f48f33

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift