threadpool: do not drop all task when calling stop.

(was pushed by mistake)

Change-Id: Id79e9759205e8e4abc2222590a1ffa588fb9bf5c
Reviewed-on: http://gerrit.aldebaran.lan/25383
Reviewed-by: cgestes <gestes@aldebaran-robotics.com>
Tested-by: cgestes <gestes@aldebaran-robotics.com>
Fix C4355 warnings: 'this' used in base initializer

Change-Id: I4651ed386511cfb3ef45f6264baefe8b7d68d43a
Reviewed-on: http://gerrit.aldebaran.lan/25446
Reviewed-by: cgestes <gestes@aldebaran-robotics.com>
Tested-by: ckilner <ckilner@aldebaran-robotics.com>
Fix unused variable warnings

Change-Id: I1f703d49e74b7f7590303e7fbe7231c6895bd0df
Reviewed-on: http://gerrit.aldebaran.lan/25445
Reviewed-by: cgestes <gestes@aldebaran-robotics.com>
Tested-by: ckilner <ckilner@aldebaran-robotics.com>