common.c: metadata support, move out nn_queue
common.c: metadata support, move out nn_queue

megahall/sdn_sensor,TidyHuang/sdn_sensor,TidyHuang/sdn_sensor,megahall/sdn_sensor,megahall/sdn_sensor,TidyHuang/sdn_sensor,TidyHuang/sdn_sensor,megahall/sdn_sensor,megahall/sdn_sensor,TidyHuang/sdn_sensor,megahall/sdn_sensor,TidyHuang/sdn_sensor,TidyHuang/sdn_sensor,megahall/sdn_sensor,TidyHuang/sdn_sensor,megahall/sdn_sensor