Add --shutdown to companion
Add --shutdown to companion

Summary: This will allow support on the client side also. We just shell out and wait for completion

Reviewed By: zeyadsalloum

Differential Revision: D20438247

fbshipit-source-id: afd0a52212550425997db8ce980e1fc6d3aa8856

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