Add liveness and readiness probes

[yorugac]

The operator currently doesn't define liveness and readiness probes. Apparently, they were added as a default in v1.3.0 of operator-sdk with a sample code:

	if err := mgr.AddHealthzCheck("healthz", healthz.Ping); err != nil {
		setupLog.Error(err, "unable to set up health check")
		os.Exit(1)
	}
	if err := mgr.AddReadyzCheck("readyz", healthz.Ping); err != nil {
		setupLog.Error(err, "unable to set up ready check")
		os.Exit(1)
	}

Confirm this behavior and add it to the operator.

[yorugac]

Related issue: #235