Merge pull request #55356 from ericchiang/cert-manager-reduce-backoff

Automatic merge from submit-queue (batch tested with PRs 54773, 52523, 47497, 55356, 49429). 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>.

certificate manager: reduce max backoff from 128s to 32s

For TLS bootstrapping in bootkube we run a kubelet with a control plane run through static pods. That static control plane has an API server and controller manager that approve the kubelet's CSR.

Since the kubelet has to wait for the static control plane to come up to be approved, we hit this backoff every time and it actually adds a notable overhead to startup times.

https://github.com/kubernetes-incubator/bootkube/pull/663

If this choice is somewhat arbitrary, I'd like to see it lowered for 1.9.

/assign @jcbsmpsn @mikedanese 

```release-note
NONE
```

staging/src/k8s.io/client-go/util/certificate/certificate_manager.go

@@ -232,7 +232,7 @@ func (m *manager) Start() {
 		Duration: 2 * time.Second,
 		Factor:   2,
 		Jitter:   0.1,
-		Steps:    7,
+		Steps:    5,
 	}
 	go wait.Forever(func() {
 		sleepInterval := m.rotationDeadline.Sub(time.Now())
@@ -240,7 +240,7 @@ func (m *manager) Start() {
 		time.Sleep(sleepInterval)
 		if err := wait.ExponentialBackoff(backoff, m.rotateCerts); err != nil {
 			utilruntime.HandleError(fmt.Errorf("Reached backoff limit, still unable to rotate certs: %v", err))
-			wait.PollInfinite(128*time.Second, m.rotateCerts)
+			wait.PollInfinite(32*time.Second, m.rotateCerts)
 		}
 	}, 0)
 }