[test_client]: serialize data according to Content-Type.
[test_client]: serialize data according to Content-Type.

Change-Id: Ibf1657cec8c8d3038ada8c3b8551f2d48c9644be

enovance/dci-control-server,redhat-cip/dci-control-server,redhat-cip/dci-control-server,enovance/dci-control-server