cmd/swarmctl: remove repeated flag definition
cmd/swarmctl: remove repeated flag definition

Signed-off-by: Stephen J Day <63efd86fa22882ae89b6027b22a36e4db1f4214d@docker.com>

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