avoid broadcasting same memberlist
avoid broadcasting same memberlist

Signed-off-by: runshenzhu <e72bf63c1c7f8bc89efcbc5c727e191b673df4f2@gmail.com>

fate-grand-order/swarmkit,diogomonica/swarmkit,docker/swarmkit,AliyunContainerService/swarmkit,dperny/swarmkit-1,elifa/swarmkit,RenaudWasTaken/swarmkit,Noyan759/swarmkit,dperny/swarmkit-1,yongtang/swarmkit,alyyousuf7/swarmkit,deljuven/swarmkit,cheyang/swarmkit,vasil-yordanov/swarmkit,runshenzhu/swarmkit,yongtang/swarmkit,AliyunContainerService/swarmkit,docker/swarmkit,alyyousuf7/swarmkit,aaronlehmann/swarmkit,sungwonh/swarmkit,allencloud/swarmkit,runshenzhu/swarmkit,diogomonica/swarmkit,sungwonh/swarmkit,elifa/swarmkit,jlhawn/swarmkit,deljuven/swarmkit,aaronlehmann/swarmkit,Noyan759/swarmkit,cezarsa/swarmkit,vasil-yordanov/swarmkit,yp-engineering/swarmkit,RenaudWasTaken/swarmkit,yp-engineering/swarmkit,cheyang/swarmkit,allencloud/swarmkit,jlhawn/swarmkit,cezarsa/swarmkit,fate-grand-order/swarmkit