Fix not allocating device_list when service appears
Fix not allocating device_list when service appears

This patch fixes an error when the tracked service disappears and
appears again. device_list hashmap is not being properly allocated.

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source