Fix support for double-inheritance of config fields.
Fix support for double-inheritance of config fields.

vishwaprakashmishra/xmatrix,vishwaprakashmishra/xmatrix,vishwaprakashmishra/xmatrix,TouK/vumi,harrissoerja/vumi,TouK/vumi,harrissoerja/vumi,TouK/vumi,harrissoerja/vumi