REST API delete build results

Problem Description

1. build result not allowed to be removed to allow merge.
2. build result not able to clear before re-running builds/test.

Suggested Solution

1. when unknown error occurs, unrelated to the tests the CI systems are running. The build result should be possible to removed to allow merge.
2. when builds/tests has failed for a commit, and the user tries to re-run said build/test. The build results should be possible to clear prior to re-running builds/tests so that there is no mix-up whether the new builds are done or not.