a2dp_source: Use SIZE_MAX queue size for worker_thread

If the queue runs out of space, we can run into a deadlock.
Explanation of the deadlock is in the bug.

If I connect and disconnect ~20 times in quick succession I would
usually run into this issue

Bug: 72121764
Test: Connect/disconnect 170 times with script, issue does not occur.
Change-Id: I0a76e51aa99481f9fe4885b879209b3d215ae5b0