Fixed crash when an iAP control session is stopped

[NicoleYarroch]

Fixes #1583

This PR is ready for review.

Risk

This PR makes no API changes.

Testing Plan

• I have verified that I have not introduced new warnings in this PR (or explain why below)
• I have run the unit tests with this PR
• I have tested this PR against Core and verified behavior (if applicable, if not applicable, explain why below).

Unit Tests

No additional test cases were added. Current unit tests passed.

Core Tests

1. Connected to a SYNC 3 v3.0 head unit and used code injection in the Xcode debugger to make the library create an iAP control session.
2. Repeatedly connected and pulled the USB cord.

Core version / branch / commit hash / module tested against: SYNC 3 v3.0
HMI name / version / branch / commit hash / module tested against: SYNC 3 v3.0

Summary

All the crash logs attached to the issue show that the crash occurs when the IAP Control Session attempts to close the output stream. I believe the issue is that the output stream's run loop was created on the lifecycle thread, which means that the lifecycle thread owns the stream. The library then closes the output stream from the main thread. Apple's documentation for streams says You should never attempt to access a scheduled stream from a thread different than the one owning the stream’s run loop.

The IAP Control Session is only created when connecting to legacy units that don't support the multisession protocol. The IAP Data Session opens and closes the streams on the ioThread, which explains why we have not seen this crash on head units that support the multisession protocol.

I changed the code to make sure the iAP control session streams are started on the main thread instead of the lifecycle thread so the streams are started and stopped on the same thread.

Changelog

Bug Fixes

• Changed the code to make sure the iAP control session streams are started and stopped on the same thread.

CLA

• I have signed the CLA

[joeljfischer]

One small change