Remove unused "containerd-addr" and "containerd-namespace" flags
Remove unused "containerd-addr" and "containerd-namespace" flags

commit fe9b06392aaa10d4aeb4a36bf4defffaa5556d96 removed the containerd executor,
as it was not currently maintained, but these two flags were left behind and are
no longer functional.

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

dperny/swarmkit-1,docker/swarmkit,dperny/swarmkit-1,docker/swarmkit