Setting a password in haproxy.cfg from an environment variable
apparently doesn't work, see: https://github.com/haproxy/haproxy/issues/590

The idea was to set the password in a Secret, whose value is passed
into the haproxy container as an env variable, using the downward API.
This will have to be redesigned.

For now we use the fixed password, so that further development is not
blocked.