Event Loop: explicity ask for stopping the io_service
Event Loop: explicity ask for stopping the io_service

Otherwise, sometimes, it may not stop!

Change-Id: Ic9275a6ada12a8cf23a44c221ff3cf9f99244e18
Reviewed-on: http://gerrit.aldebaran.lan/71124
Reviewed-by: vpaleologue <cb19838a79eb484e12a6960acfbf7c16dfdb80d9@aldebaran-robotics.com>
Reviewed-by: jlamotte <70353e7b0c7d18b7fc75605daf0ccba69fcd3222@aldebaran.com>
Tested-by: vpaleologue <cb19838a79eb484e12a6960acfbf7c16dfdb80d9@aldebaran-robotics.com>

aldebaran/libqi,aldebaran/libqi,aldebaran/libqi