import.concepts report entry is missing in JSON report

[marekhorst]

This issue is related only to JSON report representation (the value is properly stored in avro reports and exported to prometheus) and is caused by the import.concepts.duration report entry existence making the node out of the import.concepts therefore the import.concepts value is not presented in JSON file.

The easiest solution is to revert the import.concepts name back to import.concepts.total although it is not the nicest solution because we change the report name only because of the limitations of one of the report representation (JSON one).