daemon/containerd: ImageService: remove unused LookupImage()
daemon/containerd: ImageService: remove unused LookupImage()

Looks like this method was not part of the interface, and is not
used anywhere.

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

thaJeztah/docker,Ramzec/docker,jimjag/docker,nawawi/docker,jimjag/docker,trebonian/docker,moul/docker,trebonian/docker,moul/docker,Mokolea/docker,Ramzec/docker,cpuguy83/docker,thaJeztah/docker,nawawi/docker,cpuguy83/docker,Mokolea/docker,konstruktoid/docker-upstream,konstruktoid/docker-upstream,moul/docker,trebonian/docker,konstruktoid/docker-upstream,mahak/docker,jimjag/docker,Mokolea/docker,konstruktoid/docker-upstream,mahak/docker,moby/moby,jimjag/docker,mahak/docker,Ramzec/docker,thaJeztah/docker,nawawi/docker,trebonian/docker,moby/moby,moby/moby,moul/docker,mahak/docker,Ramzec/docker,nawawi/docker,cpuguy83/docker,thaJeztah/docker,cpuguy83/docker,Mokolea/docker,moby/moby