Fix haproxy backends config

[nodehatch]

What does this PR do?

It will fix the error while running docker compose up command.

Why are you doing it?

To run the HAProxy example

What are you asking the reviewer to do?

If "review", leave off.

How can the reviewer test/see/play with the changes?

If "run tests", leave off.

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R/CC: _Who should know about this change?