Compile fix for drainer test
Compile fix for drainer test

This was merged after unrelated changed made it into master that broke
compilation of the test.

Signed-off-by: Aaron Lehmann <8ecfc6017a87905413dcd7d63696a2a4c351b604@docker.com>

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