Fix self filter, checking mask value

fix self filter to work. 
this patch is confirmed on PR2 with hydro.

self_filter need to verify `keep` (mask generated by robot model) value to know if the points is inside of robot model or not.

Please checkout the codes around here: https://github.com/uos/arm_navigation/blob/master/robot_self_filter%2Finclude%2Frobot_self_filter%2Fself_see_filter.h#L264