NetworkService: quitSafely() on onDestroy()

- When IwlanNetworkService is un-bound, such as when phone app dies,
  the typical sequence is onUnbind() followed by onDestroy() immediately.
- Messages queued by onUnbind() are not processed, which leaves the
  IwlanNetworkService in an unexpected state for the next onBind().
- The change is applied to DataService.java as well for safety.

Bug: 237447534
Test:
Live test by crashing com.android.phone to verify fix to unbind/destroy
behavior.

Change-Id: I25d968867401bd7d285735c83c71e3649467c5db