Fix TSAN-detected races in ThriftServerTest.cpp
Fix TSAN-detected races in ThriftServerTest.cpp

Reviewed By: jmswen

Differential Revision: D21990566

fbshipit-source-id: 135e19b231638081395c2a7b2327ce36ac9c8e6a

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