Merge branch 'sh-fix-issue-api-perf-n-plus-one' into 'master'

Eliminate cached N+1 queries for projects in Issue API

See merge request gitlab-org/gitlab-ce!19269

changelogs/unreleased/sh-fix-issue-api-perf-n-plus-one.yml

+---
+title: Eliminate cached N+1 queries for projects in Issue API
+merge_request:
+author:
+type: performance

lib/api/issues.rb

@@ -16,7 +16,7 @@ module API
         args[:scope] = args[:scope].underscore if args[:scope]
 
         issues = IssuesFinder.new(current_user, args).execute
-          .preload(:assignees, :labels, :notes, :timelogs)
+          .preload(:assignees, :labels, :notes, :timelogs, :project)
 
         issues.reorder(args[:order_by] => args[:sort])
       end