audioflinger: do not call onTearDown() in threadLoop_exit()

This is just for MmapThread.
This change will prevent a recursive mutex lock when the teardown calls
stop() on the stream.

Bug: 66971139
Test: unplug headphones with aaudio-echo, see bugreport
Change-Id: I904a8e575bbc5ae8b03350c061dd23cba62783f0
1 file changed