aaudio: fix intermittent hang and position error

Fix hang caused by recursive mutex.
Fix disconnect caused by getPosition() failing, which was
just because the stream wasn't ready yet.

Bug: 63775537
Bug: 63709749
Test: run "aaudio_loopback -pl -Pl -c2 -n6 -te -m" many times
Change-Id: Ic1d54360b55cfc8ecc1809584c262bc0976c58bb