Make errors in the cluster list function visible.

Sometimes the operator does not pick up clusters right away when
they are created. The change attempts to shed light on the
reason behind that.

pkg/controller/postgresql.go

@@ -30,8 +30,7 @@ func (c *Controller) clusterResync(stopCh <-chan struct{}, wg *sync.WaitGroup) {
 	for {
 		select {
 		case <-ticker.C:
-			_, err := c.clusterListFunc(metav1.ListOptions{ResourceVersion: "0"})
-			if err != nil {
+			if _, err := c.clusterListFunc(metav1.ListOptions{ResourceVersion: "0"}); err != nil {
 				c.logger.Errorf("could not list clusters: %v", err)
 			}
 		case <-stopCh:
@@ -52,9 +51,12 @@ func (c *Controller) clusterListFunc(options metav1.ListOptions) (runtime.Object
 
 	b, err := req.DoRaw()
 	if err != nil {
+		c.logger.Errorf("could not get the list of postgresql CRD objects: %v", err)
 		return nil, err
 	}
-	err = json.Unmarshal(b, &list)
+	if err = json.Unmarshal(b, &list); err != nil {
+		c.logger.Warningf("could not unmarshal list of clusters: %v", err)
+	}
 
 	if time.Now().Unix()-atomic.LoadInt64(&c.lastClusterSyncTime) <= int64(c.opConfig.ResyncPeriod.Seconds()) {
 		return &list, err