[osxsink/iossink] - don't block addpackets if ca didn't do the initial d...

...ata pull - but timeout gracefully for signaling an error condition to the engine (use a timer for detecting a real timeout as condvar can be signaled by spurious interrupts)

This should fix a race/deadlock when unplugging cables/switching of amp/tv ...

Backport of #4322

Please wait for my go.