Changed location of Watson Studio logs

The Watson Studio logs from the dataplatform-service node service are moved from a separate directory to the centralized cognosserver.log file.

The logs are now written to the install_location/logs/cognosserver.log file.

In previous versions of IBM Cognos Analytics with Watson, the logs for the dataplatform-service node service were in the install_location/node-services/ca-dataplatform-service/logs directory.