remove unused variable - once
remove unused variable - once

Signed-off-by: Xian Chaobo <dcd6fd1596156638bd4b273477ce808661e40b45@huawei.com>

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