BassClientService: Add missing return if source add failed

Fix unit tests for intentional and unintentional disconnection
by setting correct playing state for local broadcast.

Remove unnecessary broadcast searching as these tests are only
for local broadcast.

Bug: 338574075
Bug: 333050419
Test: atest BassClientServiceTest
Change-Id: Ic433405954491ab9ab475160e55e3aa6d91b3b27