Exit bt process after cleanup

Added code to exit bt process and avoid android process caching.
The fix also gives end user a chance to recover a bad state bt process by
simply turning off/on the bluetooth. Since the process is not recycled,
the kernel frees up all leftover fd and  memory and gives bt process a fresh start every time.

Change-Id: I616345da70bb60f1aeaab151a6bf6f793168a829