Always eagerly load an issue's author.

Rather radical but avoids n+1 queries in the rather common case we want
to include information about the author.

app/finders/issues_finder.rb

@@ -21,7 +21,7 @@ class IssuesFinder < IssuableFinder
   CONFIDENTIAL_ACCESS_LEVEL = Gitlab::Access::REPORTER
   def klass
-    Issue
+    Issue.includes(:author)
   end
   def with_confidentiality_access_check