As of https://github.com/kubernetes/kubernetes/pull/72831, the minimum
docker version is 1.13.1. (and the minimum API version is 1.26). The
only time the `RuntimeAdmitHandler` returns anything other than accept
is when the Docker API version < 1.24. In other words, we can be
confident that Docker will always support sysctl.
As a result, we can delete this unnecessary and docker-specific code.
In order to make it compilable I had to remove these files manually:
pkg/client/listers/extensions/internalversion/podsecuritypolicy.go
pkg/client/informers/informers_generated/internalversion/extensions/internalversion/podsecuritypolicy.go
pkg/client/clientset_generated/internalclientset/typed/extensions/internalversion/podsecuritypolicy.go
pkg/client/clientset_generated/internalclientset/typed/extensions/internalversion/fake/fake_podsecuritypolicy.go
