Merge pull request #51698 from rphillips/feat/lease_endpoint_reconciler

Automatic merge from submit-queue (batch tested with PRs 52240, 48145, 52220, 51698, 51777). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>..

add lease endpoint reconciler

**What this PR does / why we need it**: Adds OpenShift's LeaseEndpointReconciler to register kube-apiserver endpoints within the storage registry.

Adds a command-line argument `alpha-endpoint-reconciler-type` to the kube-apiserver.

Defaults to the old MasterCount reconciler.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes kubernetes/community#939 fixes kubernetes/kubernetes#22609

**Release note**:
```release-note
Adds a command-line argument to kube-apiserver called
--alpha-endpoint-reconciler-type=(master-count, lease, none) (default
"master-count"). The original reconciler is 'master-count'. The 'lease'
reconciler uses the storageapi and a TTL to keep alive an endpoint within the
`kube-apiserver-endpoint` storage namespace. The 'none' reconciler is a noop
reconciler that does not do anything. This is useful for self-hosted
environments.
```

/cc @lavalamp @smarterclayton @ncdc

pkg/master/master_test.go

@@ -58,6 +58,7 @@ import (
 	"k8s.io/kubernetes/pkg/apis/extensions"
 	"k8s.io/kubernetes/pkg/apis/rbac"
 	kubeletclient "k8s.io/kubernetes/pkg/kubelet/client"
+	"k8s.io/kubernetes/pkg/master/reconcilers"
 	certificatesrest "k8s.io/kubernetes/pkg/registry/certificates/rest"
 	corerest "k8s.io/kubernetes/pkg/registry/core/rest"
 	"k8s.io/kubernetes/pkg/registry/registrytest"
@@ -76,6 +77,7 @@ func setUp(t *testing.T) (*etcdtesting.EtcdTestServer, Config, informers.SharedI
 			APIResourceConfigSource: DefaultAPIResourceConfigSource(),
 			APIServerServicePort:    443,
 			MasterCount:             1,
+			EndpointReconcilerType:  reconcilers.MasterCountReconcilerType,
 		},
 	}