cert-manager: Cache only kubemacpool secrets (#426)

The webhook secrets and services at kubemacpool are living under
kubemacpool namespace, this change limit cert-manager reconciler to that
so it will not cache secrets at all namespaces.

Signed-off-by: Enrique Llorente <ellorent@redhat.com>

cmd/manager/main.go

@@ -77,7 +77,8 @@ func runCertManager() {
 	}
 
 	mgrOptions := ctrlmanager.Options{
-		MetricsBindAddress: "0", // disable metrics
+		MetricsBindAddress: "0",          // disable metrics
+		Namespace:          podNamespace, // cache only the secrets from kubemacpool namespace
 	}
 
 	mgr, err := ctrlmanager.New(config.GetConfigOrDie(), mgrOptions)