Fix api-gen-docs dependencies

[mikesplain]

Currently it looks like api-gen-docs on a clean system doesn't grab all the required components:

docker run -it -v $(pwd):/go/src/k8s.io/kops -w /go/src/k8s.io/kops golang make gen-api-docs

# Follow procedure in docs/apireference/README.md
hack/make-gendocs.sh
# Update the `pkg/openapi/openapi_generated.go`
/go/bin/apiserver-boot build generated --generator openapi --copyright hack/boilerplate/boilerplate.go.txt
make: /go/bin/apiserver-boot: Command not found
Makefile:347: recipe for target 'gen-api-docs' failed
make: *** [gen-api-docs] Error 127

This pr should at least fix that issue and allow us to focus on this error (#5387) more easily.

docker run -it -v $(pwd):/go/src/k8s.io/kops -w /go/src/k8s.io/kops golang make gen-api-docs                                                                                                                                                                                                                                                                     system
# Follow procedure in docs/apireference/README.md
hack/make-gendocs.sh
# Update the `pkg/openapi/openapi_generated.go`
/go/bin/apiserver-boot build generated --generator openapi --copyright hack/boilerplate/boilerplate.go.txt
/go/bin/openapi-gen --input-dirs k8s.io/kops/pkg/apis/kops/v1alpha1 --input-dirs k8s.io/kops/pkg/apis/kops/v1alpha2 --input-dirs k8s.io/kops/pkg/apis/kops -o /go/src --go-header-file hack/boilerplate/boilerplate.go.txt -i k8s.io/apimachinery/pkg/apis/meta/v1,k8s.io/apimachinery/pkg/api/resource,k8s.io/apimachinery/pkg/version,k8s.io/apimachinery/pkg/runtime,k8s.io/apimachinery/pkg/util/intstr,k8s.io/api/admission/v1beta1,k8s.io/api/admissionregistration/v1alpha1,k8s.io/api/admissionregistration/v1beta1,k8s.io/api/apps/v1,k8s.io/api/apps/v1beta1,k8s.io/api/apps/v1beta2,k8s.io/api/authentication/v1,k8s.io/api/authentication/v1beta1,k8s.io/api/authorization/v1,k8s.io/api/authorization/v1beta1,k8s.io/api/autoscaling/v1,k8s.io/api/autoscaling/v2beta1,k8s.io/api/batch/v1,k8s.io/api/batch/v1beta1,k8s.io/api/batch/v2alpha1,k8s.io/api/certificates/v1beta1,k8s.io/api/core/v1,k8s.io/api/events/v1beta1,k8s.io/api/extensions/v1beta1,k8s.io/api/imagepolicy/v1alpha1,k8s.io/api/networking/v1,k8s.io/api/policy/v1beta1,k8s.io/api/rbac/v1,k8s.io/api/rbac/v1alpha1,k8s.io/api/rbac/v1beta1,k8s.io/api/scheduling/v1alpha1,k8s.io/api/settings/v1alpha1,k8s.io/api/storage/v1,k8s.io/api/storage/v1alpha1,k8s.io/api/storage/v1beta1,k8s.io/client-go/pkg/apis/clientauthentication/v1alpha1,k8s.io/api/core/v1 --output-package k8s.io/kops/pkg/openapi
go install k8s.io/kops/cmd/kops-server
/go/bin/apiserver-boot build docs --disable-delegated-auth=false --output-dir docs/apireference --server kops-server
2018/07/24 17:37:43 kops-server --etcd-servers=http://localhost:2379 --secure-port=9443 --print-openapi
W0724 17:37:44.538096    5603 authorization.go:34] Authorization is disabled
W0724 17:37:44.538196    5603 authentication.go:55] Authentication is disabled
E0724 17:37:44.541138    5603 cacher.go:271] unexpected ListAndWatch error: storage/cacher.go:/kops/instancegroups: Failed to list *kops.InstanceGroup: client: etcd cluster is unavailable or misconfigured; error #0: dial tcp 127.0.0.1:2379: connect: connection refused
E0724 17:37:44.541160    5603 cacher.go:271] unexpected ListAndWatch error: storage/cacher.go:/kops/clusters: Failed to list *kops.Cluster: client: etcd cluster is unavailable or misconfigured; error #0: dial tcp 127.0.0.1:2379: connect: connection refused
W0724 17:37:44.541677    5603 genericapiserver.go:342] Skipping API kops/v1alpha1 because it has no resources.
2018/07/24 17:37:44 /go/bin/gen-apidocs --build-operations=false --use-tags=true --allow-errors --config-dir=docs/apireference
Could not load json file docs/apireference/openapi-spec/swagger.json as api-spec: json: cannot unmarshal array into Go struct field SwaggerProps.paths of type map[string]json.RawMessage
2018/07/24 17:37:44 error: exit status 1
Makefile:347: recipe for target 'gen-api-docs' failed
make: *** [gen-api-docs] Error 1

[chrisz100]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chrisz100, mikesplain

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [mikesplain]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment