Consul service throws error on fresh install when using `monitoring_service_discovery`

Feature was added in !3295 (merged) but causes the following error on fresh installs if monitoring_service_discovery is set before the first reconfigure:

consul_service[rails] (gitlab::unicorn line 31) had an error: 
Chef::Exceptions::UserIDNotFound: file[/var/opt/gitlab/consul/config.d/rails-service.json] 
(/opt/gitlab/embedded/cookbooks/cache/cookbooks/consul/resources/consul_service.rb line 38) had an error: 
Chef::Exceptions::UserIDNotFound: cannot determine user id for 'gitlab-consul', does the user exist on this system?

This service is called from several reciples, including gitlay, sidekiq, etc. And all the CE recipes will be called before the consule recipe, which is where the consul user is created.