Automatic merge from submit-queue
Non global admission plugin registry
For testing the global state is a problem. This PR turns the actual registry into a struct that must be instantiated. For the beginning, we do this in `pkg/kubeapiserver/admission`. In some follow-up (where we hunt down all globals some day), we will move this into the genericapiserver.
The exported or public functions requires a doc comment to pass golint.
This commit has changes of conversion generated code. The actual doc
changes are added into a separate commit for a clean review.
