Verified that on 5.7.3.1 meaningful result is returned when deleting orchestration templates: {"results":[{"success":true,"message":"orchestration_templates id: 50 deleting","href":"https://<ip>/api/orchestration_templates/50"},{"success":true,"message":"orchestration_templates id: 51 deleting","href":"https://<ip>/api/orchestration_templates/51"}]}
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHSA-2017:1601