aaudio: cleanup code that reads timing model

Only use the clock model for the position when
it is running and when the service is not updating
the FIFO counter.

Bug: 120932593
Bug: 122374244
Test: test_return_stop
Test: test_return_stop -i
Change-Id: I6d6a23b35dca5529b6221e1b3b4a4e6672093bf2
6 files changed