Fix stage status shown for pipelines

## What does this MR do?
Properly calculates a status of stage when shown on a list of pipelines

## Why was this MR needed?
Previously we were calculating a status for all builds, including retried ones. 
This were affecting a overall stage status when a build were retried.

## What are the relevant issue numbers?
Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/18896 https://gitlab.com/gitlab-org/gitlab-ce/issues/18150

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5277