audiopolicy: remove audioserver died from audio volume group callback

Bug: 293236285
Flag: EXEMPT refactor
Test: adb shell killall audioserver & ensure callback is still
received by the client

Change-Id: I28d9dba59d2c4d61ba701ec5dbbf8681d6cbd8fe
Signed-off-by: François Gaffie <francois.gaffie@renault.com>