Import export users select

What does this MR do?

EE port: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1886

This is an attempt to fix this transient that pops up frequently.

https://gitlab.com/gitlab-org/gitlab-ce/builds/16056917

This is an experimental fix. This fix isn't based on any formal debugging because this is a very strange issue. After looking into how we use UsersSelect, I noticed it could be improved and we can see if this makes those specs any more stable.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?