API call for deleting an environment gives 404

Summary

A call to https://docs.gitlab.com/ce/api/enviroments.html#delete-an-environment using the ID received using https://docs.gitlab.com/ce/api/enviroments.html#list-environments returns a 404 status

Steps to reproduce

• GitLab 8.15.2 https://github.com/sameersbn/docker-gitlab
• Use the mentioned API call to receive the environment ID https://docs.gitlab.com/ce/api/enviroments.html#delete-an-environment
• Use the mentioned API call to delete the environment https://docs.gitlab.com/ce/api/enviroments.html#list-environments

Expected behavior

The environment should be deleted

Actual behavior

The response is a 404 status, and the environment still exists.

Additional remarks

This is not #24147 (closed) I really want to delete some environments. Deleting an environment is also missing in the UI https://.../environments/1/edit