AAudio: fix NotificationClient linkToDeath error

Enhance the handling of race condition, otherwise when it happens, there
is the possibility that no death monitor is linked to the binder for the
new client due to the binder was not set in the NotificationClient
instance, hence when that client dies, there would be no way to inform
audio framework to close its stream.

Submitted on behalf of Laiwen.Zhu@gm.com

Bug: 381398054
Test: manual test with mobile devices
Flag: EXEMPT bugfix
Change-Id: Id9fca4a998b1a3a553e618428f243e54c5f6717a