Fix for open-ended parameter's in lograge causing elastic memory issues

What does this MR do?

See https://gitlab.com/gitlab-com/infrastructure/issues/2888 See https://gitlab.com/gitlab-org/gitlab-ce/issues/43678 See gitlab-com/migration#163 (closed)

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

This is how the JSON logs look now:

{
  "method":"GET",
  "path":"/",
  "format":"html",
  "controller":"RootController",
  "action":"index",
  "status":200,
  "duration":3920.51,
  "view":3415.83,
  "db":31.85,
  "time":"2018-02-28T12:01:45.981Z",
  "params":[{"key":"moo","value":"foo"}],
  "remote_ip":"127.0.0.1",
  "user_id":27,
  "username":"moo"
}

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
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?