Rails5: env is deprecated and will be removed from Rails 5.1

What does this MR do?

Replace deprecated env with request.env for Rails 5. See https://github.com/rails/rails/commit/05934d24aff62d66fc62621aa38dae6456e276be#diff-4150e8175b9a99c0e92bfdcaabf8455d and https://github.com/rails/rails/issues/23294#issuecomment-175914159

What are the relevant issue numbers?

Fix #54384 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.