AudioSystem: more locking work on audio device callback

commit 24a9fb0d left some locking issues with management of device
callbacks in AudioSystem, AudioTrack and AudioRecord.

This change makes that the AudioSystem mutex is not held when
callbacks are called into AudioTrack and AudioRecord removing cross
deadlock risks and allowing AudioRecord and AudioTrack to hold their
mutexes while installing and handling the callbacks

Test: CTS RoutingTest, AudioTrackTest, AudioRecordTest
Change-Id: I5d17e77ca26220092deb0bd6e5a33dc32348d460