Ensure that subprocess has terminated in companion shell-out
Ensure that subprocess has terminated in companion shell-out

Summary:
This means that we don't get an erroneous exit-code on the cli-wrapper.

Before the work was being performed correctly and re-parented when the cli died, but that this was propogating the wrong information

Reviewed By: c-ryan747

Differential Revision: D20515642

fbshipit-source-id: 700606050f618b133a269238539e883701b70401

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