fix instruments_run race crash
fix instruments_run race crash

Reviewed By: lawrencelomax

Differential Revision: D16221442

fbshipit-source-id: c9043bd997961fe5b80e84b54de5b048f73920b2

facebook/FBSimulatorControl,facebook/FBSimulatorControl,facebook/FBSimulatorControl,facebook/FBSimulatorControl,facebook/FBSimulatorControl