Fix MR 500 when viewing the MR page
I did spot a two of problems:
- ci_build_details_page had different implementation in EE which lead to the 500
- I did deprecate the GitLabCiService, but it could still be picked as "active" CI Service due to fact that had active flag set
The both problems are resolved. The mentioned part of code is cherry-picked to GitLab CE codebase.
@rspeicher You will get a merge conflict when you try to merge it back to GitLab EE, but the fix is simple.
/cc @dblessing
Fixed #2712 (closed)