Fix test of add_tag_to_msg to match new behaviour (i.e. tags are always stored as a list inside the message payload).
Fix test of add_tag_to_msg to match new behaviour (i.e. tags are always stored as a list inside the message payload).

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