A2DP: Don't wait for role switch on a blacklisted device

When there are 2 or more ACL links, we will try to be the master for
better link quality, and setup flags to wait for the following role
switch results. Because this is an asynchronous task, we would check
flags for any further actions. However, there would not be other results
for role switch IOP, and could be just ignored.

Bug: 141177108
Test: Add headset to IOP and do A2DP playback manually
Change-Id: I0d9e92968765365410909908ffcaf6dc81161ea0