Revisit activerecord patches we have added when we hit rails 5
This was brought up from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13560 which we added yet another patch, which was also somehow based on some changes on Rails 5. We should revisit them when we hit Rails 5.
Also, check if Rails 5 requires similar patch as we added: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13560#note_37607286 Because their patch doesn't mention the magical CURRENT_TIMESTAMP
at all, and that's what we're really patching for.
This is for now blocked by https://gitlab.com/gitlab-org/gitlab-ce/issues/14286
/cc @yorickpeterse