Correctly detect dead soundtrigger HAL process

This is a follow-up to b/160169016, which changes how
HwBinder presents a dead server to the client.

Test: Changed the code to cause the HAL process do occasionally die in
the middle of a call and observed the logs to verify that the death is
recognized correctly and recovered from.

Change-Id: Ic510fa6cbafa4cee5c53a5a6a28823c34c3d05c1