Allow sandbox_protocol_for_message to resturn a deferred.
Allow sandbox_protocol_for_message to resturn a deferred.

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