Make audiohal service 'oneshot' to avoid double restart on crash

audioserver receives a change that makes it to crash once it
detects that audiohal server has crashed (because audioflinger
can't gracefully restore the state of the audio system).

As audioserver.rc file prescribes restaring the audiohal on
audioserver restart, there is no need to rely on the init process
to restart the audiohal. Moreover, asking the init process to do
that causes a double restart of the audiohal service if it crashes.

Test: kill audio-hal process, watch dmesg and logcat
Change-Id: Iac4cc79cdc1a3debd2b9cfcdf42f11451d7ce24c