prometheus: Initialize mgmt_checkapply_total metrics

It is recommended by Prometheus to initialize metrics:

https://prometheus.io/docs/practices/instrumentation/#avoid-missing-metrics

This commits initialize the mgmt_checkapply_total metric
for each registered resource.

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

resources/resources_test.go

@@ -78,6 +78,18 @@ func TestIFF(t *testing.T) {
 	}
 }
 
+func TestRegisteredResourcesNames(t *testing.T) {
+	kinds := RegisteredResourcesNames()
+	for _, kind := range kinds {
+		if kind == "" {
+			t.Error("Empty kind found")
+		}
+	}
+	if len(kinds) == 0 {
+		t.Error("No registered resources")
+	}
+}
+
 func TestReadEvent(t *testing.T) {
 	//res := FileRes{}