Fix exit with no error when cert violates lookahead (#2395)

Add an exit message when the certificate check triggers a fatal exit
(via cancel()). When cancel() is called, this cancels the main
context which causes the webhook to shutdown.

A return is also added to ensure the message "valid" comes out right
after "invalid" like so:

"certs are not valid at..."
"certs are valid"

Signed-off-by: Eric Stokes <fernferret@gmail.com>

cmd/webhook.go

@@ -98,7 +98,9 @@ var webhookCmd = &cobra.Command{
 					setupLog.Info("validating certs")
 					err = crds.CheckCerts(c, dnsName, time.Now().Add(certLookaheadInterval))
 					if err != nil {
+						setupLog.Error(err, "certs are not valid at now + lookahead, triggering shutdown", "certLookahead", certLookaheadInterval.String())
 						cancel()
+						return
 					}
 					setupLog.Info("certs are valid")
 				}