health: return HTTP 404 when in maintenance mode
health: return HTTP 404 when in maintenance mode

cf http://cbonte.github.io/haproxy-dconv/1.6/configuration.html#4.2-http-check%20disable-on-404

olaurendeau/v6_ui,Courgetteandratatouille/v6_ui,olaurendeau/v6_ui,Courgetteandratatouille/v6_ui,c2corg/v6_ui,Courgetteandratatouille/v6_ui,olaurendeau/v6_ui,c2corg/v6_ui,c2corg/v6_ui,olaurendeau/v6_ui,c2corg/v6_ui,Courgetteandratatouille/v6_ui