horizon::vhost_extra_params is already configured in puppet/services/horizon.yaml, and users can change the value with HorizonVhostExtraParams parameter. Docker deployments didn't have HorizonVhostExtraParams taken in account since we were overriding with Hiera. This patch fix it. Closes-Bug: #1749627 Change-Id: I77f1312112c7f613d795242060709082ef72f150