Disable environment list polling as it breaks deployboard

What does this MR do?

Since the environment list refresh does break Deployboards, and there's no quick fix as of now to fix environment list I decided to selectively disable polling that we introduced: https://gitlab.com/gitlab-org/gitlab-ee/issues/2677.

We should revert this change as soon as we fix the bug.

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?