fix controller Start method signature

Signed-off-by: Roland.Ma <rolandma@yunify.com>

pkg/controller/certificatesigningrequest/certificatesigningrequest_controller.go

@@ -240,8 +240,8 @@ func (c *Controller) reconcile(key string) error {
 	return nil
 }
 
-func (c *Controller) Start(stopCh <-chan struct{}) error {
-	return c.Run(4, stopCh)
+func (c *Controller) Start(ctx context.Context) error {
+	return c.Run(4, ctx.Done())
 }
 
 func (c *Controller) Approve(csr *certificatesv1beta1.CertificateSigningRequest) error {