wpa: Terminate on callback client death

supplicant/hostapd are single client HAL's. So, the daemon should
terminate when the client is dead.

Also, removed a bunch of TODO's/#ifdef guarding death notification
handling in supplicant.

Bug: 169651797
Test: Manual
i) adb shell stop
ii) Ensure wpa_supplicant is killed (via ps-ef & lshal)

Change-Id: I0d32f2a91cbe807145fe0c544460467ff24fa2cc
4 files changed