Update to Xcode 9.1
Update to Xcode 9.1

Summary: We're lagging on test quality. First step is to update to the latest Xcode.

Reviewed By: antiarchit

Differential Revision: D6271453

fbshipit-source-id: d55c507e09d8d7dfc0f289e13d02bdfaafa54e76

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