fix issue #121, unload plugins, stop/start gproc app when clustering...
fix issue #121, unload plugins, stop/start gproc app when clustering...

AcmHacker/emqttd,fsxchen/emqttd,Inner-room/emqttd,wwezhuimeng/emqtt,yanyanqin/emqttd,sunilkumartc/ermqtt,codertrack/emqttd,wwezhuimeng/emqtt,kimiscircle/emqttd,joaohf/emqttd,kimiscircle/emqttd,tempbottle/emqttd,yocome/emqttd,sunilkumartc/ermqtt,janshahid/jmq,yangchaogit/emqttd,sureddy/emqttd,shaominghaoo/emqttd,wwezhuimeng/emqtt,mickelfeng/emqttd,gxbllm/emqttd,santuoshi/emqttd,sunilkumartc/ermqtt,jfjalburquerque/emqttd,neviim/emqttd,guidao/emqttd,fengshao0907/emqttd,kimiscircle/emqttd,lianghaivv/emqttd