Since service clients need to be migrated to Tempest-lib, they should
not truncate any things from API response. Current DataProcessing client
cuts out the top key of a response and returns only value to the caller.
All service clients should return the response as they get it from APIs.
Change-Id: I0d2d47db0ccfb306269a60557c4e510082ad0d3e
Partially-implements: blueprint method-return-value-and-move-service-clients-to-lib
1662b0e27a