hack: remove integration-cli-on-swarm

integration-on-swarm had unnecessary complexity and was too hard to
maintain. Also, it didn't support the new non-CLI integration test suite.

I'm now doing some experiments out of the repo using Kubernetes:
https://github.com/AkihiroSuda/kube-moby-integration

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

.dockerignore

@@ -3,5 +3,4 @@ bundles
 vendor/pkg
 .go-pkg-cache
 .git
-hack/integration-cli-on-swarm/integration-cli-on-swarm