[audio] Handle DEAD_OBJECT from system server

Aborting when a transaction with system server fails with dead object
leads to misattributed native stack traces. Since the system will soon
be restarted regardless, softly tolerate this failure within
audioserver.

Test: compiles
Flag: EXEMPT bug fix
Fixes: 390298225
Change-Id: Idb3bfae0c0376e884f8771abd0d1ce8695cd9c07