Returning error message when image pull fails
Returning error message when image pull fails

Signed-off-by: Nishant Totla <18d513b5cc13a17570075e17ff7a4e1db98175e4@gmail.com>

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