Fix BackupSession's Print Columns (#11)

Author: hossainemruz

docs/elasticsearch.md

@@ -362,10 +362,10 @@ Wait for the next schedule. Run the following command to watch `BackupSession` c
 
 ```console
 $ kubectl get backupsession -n demo -w
-NAME                                     BACKUPCONFIGURATION           PHASE     AGE
-sample-elasticsearch-backup-1570098367   sample-elasticsearch-backup   Running   9s
-sample-elasticsearch-backup-1570098367   sample-elasticsearch-backup   Running   79s
-sample-elasticsearch-backup-1570098367   sample-elasticsearch-backup   Succeeded   79s
+NAME                                     INVOKER-TYPE          INVOKER-NAME                  PHASE       AGE
+sample-elasticsearch-backup-1570098367   BackupConfiguration   sample-elasticsearch-backup   Running     9s
+sample-elasticsearch-backup-1570098367   BackupConfiguration   sample-elasticsearch-backup   Running     65s
+sample-elasticsearch-backup-1570098367   BackupConfiguration   sample-elasticsearch-backup   Succeeded   79s
 ```
 
 We can see above that the backup session has succeeded. Now, we are going to verify that the backed up data has been stored in the backend.