Use -[FBTask exitCode] rather than -[FBTask completed] in FBXCTraceOperation
Use -[FBTask exitCode] rather than -[FBTask completed] in FBXCTraceOperation

Summary:
This can be done as:

1) When the task is created, no exit codes are passed to the builder, meaning that the default of 0 being the only acceptible code is the correct one.
2) Cancellation behaviour of -[FBTask completed] is not depended on, there's an override of the cancellation behaviour on purpose.

Reviewed By: jamescoggan

Differential Revision: D30250185

fbshipit-source-id: 3769548c0167234bb99fda648dcdd6c612e3cde6

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