Manually set MR head_pipeline on approvals test

Related to https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10064

spec/features/merge_requests/approvals_spec.rb

@@ -251,7 +251,8 @@ feature 'Merge request approvals', js: true, feature: true do
     context 'when CI is running but no approval given', js: true do
       before do
         create :approver_group, group: group, target: merge_request
-        create(:ci_empty_pipeline, project: project, sha: merge_request.diff_head_sha, ref: merge_request.source_branch)
+        pipeline = create(:ci_empty_pipeline, project: project, sha: merge_request.diff_head_sha, ref: merge_request.source_branch)
+        merge_request.update(head_pipeline: pipeline)
         visit namespace_project_merge_request_path(project.namespace, project, merge_request)
       end