Fixed rendering of XML attributes into JSON elements in A-REX REST response.

Begin arcbot message
This merge request is automatically cherrypicked from !1699 (merged) from source branch https://source.coderefinery.org/aleksandr.konstantinov/arc/-/tree/fix_info_json_rendering orginally made by @aleksandr.konstantinov .
The original MR went to branch: https://source.coderefinery.org/nordugrid/arc/-/tree/next
End arcbot message