Support completions for --clusterrole of kubectl create clusterrolebinding

[superbrothers]

What this PR does / why we need it:
This PR supports completion for --clusterrole of kubectl create clusterrolebinding.

$ kubectl create clusterrolebinding hoge --clusterrole <tab>
admin                                         system:controller:daemon-set-controller       system:controller:node-controller             system:controller:service-controller          system:kube-scheduler
cluster-admin                                 system:controller:deployment-controller       system:controller:persistent-volume-binder    system:controller:statefulset-controller      system:node
edit                                          system:controller:disruption-controller       system:controller:pod-garbage-collector       system:controller:ttl-controller              system:node-bootstrapper
system:auth-delegator                         system:controller:endpoint-controller         system:controller:replicaset-controller       system:discovery                              system:node-problem-detector
system:basic-user                             system:controller:generic-garbage-collector   system:controller:replication-controller      system:heapster                               system:node-proxier
system:controller:attachdetach-controller     system:controller:horizontal-pod-autoscaler   system:controller:resourcequota-controller    system:kube-aggregator                        system:persistent-volume-provisioner
system:controller:certificate-controller      system:controller:job-controller              system:controller:route-controller            system:kube-controller-manager                view
system:controller:cronjob-controller          system:controller:namespace-controller        system:controller:service-account-controller  system:kube-dns

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

I feel that it is better to except system clusterroles from completion candidates. What do you think about it?

Release note:

Support completion for --clusterrole of kubectl create clusterrolebinding

[k8s-ci-robot]

Hi @superbrothers. Thanks for your PR.

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[cblecker]

/ok-to-test

[shiywang]

/assign

[shiywang]

@superbrothers sorry, I tried this command kubectl create clusterrolebinding test --clusterrole [TAB] with bash, but it doesn't works, is there anything wrong with my settting ?

[root@shiywang kubernetes]# echo $SHELL
/bin/bash

[root@shiywang kubernetes]# kubectl get clusterrole
NAME            AGE
secret-reader   2m

[root@shiywang kubernetes]# kubectl get nodes
NAME       STATUS    AGE       VERSION
minikube   Ready     22m       v1.7.0

[root@shiywang kubernetes]# kubectl create clusterrolebinding test123 --clusterrole --->TAB doesn't complete, but I have a clusterrole secret-reader right ?
api/                           docs/                          .idea/                         plugin/
_artifacts/                    examples/                      labels.yaml                    README.md
.bazelrc                       federation/                    LICENSE                        staging/
build/                         .gazelcfg.json                 logo/                          test/
BUILD.bazel                    .generated_files               .make/                         third_party/
CHANGELOG.md                   .git/                          Makefile                       translations/
cluster/                       .gitattributes                 Makefile.generated_files       Vagrantfile
cmd/                           .github/                       _output/                       vendor/
code-of-conduct.md             .gitignore                     OWNERS                         WORKSPACE
CONTRIBUTING.md                Godeps/                        OWNERS_ALIASES                 
.dockerized-kube-version-defs  hack/                          pkg/                           

[root@shiywang kubernetes]# kubectl version
Client Version: version.Info{Major:"1", Minor:"8+", GitVersion:"v1.8.0-alpha.1.572+703c3b93448b15", GitCommit:"703c3b93448b1565c6ed4bde47dfedca85ddf53a", GitTreeState:"clean", BuildDate:"2017-07-31T06:42:44Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"7", GitVersion:"v1.7.0", GitCommit:"d3ada0119e776222f11ec7945e6d860061339aad", GitTreeState:"clean", BuildDate:"2017-06-30T10:17:58Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}

[superbrothers]

@shiywang Did you source the shell code outputed by kubectl completion bash? I tested on both bash and zsh.

$ bash --version
GNU bash, version 4.3.48(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ . /home/ksuda/.linuxbrew/etc/bash_completion
$ go build -o kubectl cmd/kubectl/kubectl.go
$ source <(./kubectl completion bash)
$ kubectl get clusterrole
NAME            KIND
secret-reader   ClusterRole.v1beta1.rbac.authorization.k8s.io
$ kubectl create clusterrolebinding test123 --clusterrole <TAB> # TAB complete `secret-reader` :)

[superbrothers]

@shiywang ping

[superbrothers]

@eparis @rootfs @shiywang Would you please review this PR?

[eparis]

/lgtm
/retest
/approve no-issue

[eparis]

/assign @brendandburns
super easy one brendan.

[brendandburns]

/approve no-issue

[k8s-github-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: brendandburns, eparis, superbrothers

Associated issue requirement bypassed by: brendandburns

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[k8s-github-robot]

/test all

Tests are more than 96 hours old. Re-running tests.

[k8s-github-robot]

/test all [submit-queue is verifying that this PR is safe to merge]

[k8s-github-robot]

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions here.