Add support for not storing __cache__ on VumiMessages.
Add support for not storing __cache__ on VumiMessages.

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