libsysutils: Get rid of warnings

- UNUSED argument warnings
- Remove LOG_NDEBUG define

(cherry picked from commit 696f267ff5a1e6227c2f5784dae60c190e0228b8)

Change-Id: I48b0942adfdb7a46a7693e580bc6ed5a685b0d5b
libsysutils: SocketListener export release

* Foreground thread (legacy) closes connection by
  reporting false return value for onDataAvailable.
* Background thread can choose instead to close the
  connection asynchronously by calling release, must
  return true for the onDataAvailable method.

(cherry picked from commit d7ad4e409eaac53db3a9789060097b712850b337)

Change-Id: I70ab37d5c22b02804aa3b4dfb26cc9b75291f8b6