[DDF] remove kie-server from the url as this is not part of the default configuration. And the header should be Content-type

remove kie-server from the url as this is not part of the default configuration. And the header should be Content-type and not Accept, otherwise the server fails

Reported by: lucamaf

https://access.redhat.com/documentation/en-us/red_hat_process_automation_manager/7.6/html/managing_and_monitoring_process_server/prometheus-monitoring-con_execution-server#annotations:1c2440b3-8f44-4476-90b1-8190d8e78ca9