For Android Source exampl, fixed sink add/remove adapter calls to run on UI thread.

Change-Id: Ia9ff091b26fa54d7c1119f55edad8d0b55e11c38
AJAUDIO-19: Increase concurrency of client to handle receiving
Announce signals from a large number of services.

Previous fix to call FindAdvertisedName asynchronously was
insufficient.

Change-Id: If614a9acd927e49d89f1d343c2c914db6f4bc55a