Remove dispatch_get_main_queue from FBiOSActionReader
Remove dispatch_get_main_queue from FBiOSActionReader

Summary: Use the `serializationQueue` for work instead of the main queue, this means that it will be possible to change the queue that this work is performed on in future

Reviewed By: c-ryan747

Differential Revision: D5619679

fbshipit-source-id: 9395156cd14e6372b9e80fee32dcc2afb7189d25

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