added more variables to the cluster variables section of the advanced install

Author: bfallonf

install_config/install/advanced_install.adoc

@@ -306,6 +306,18 @@ re-configured after deployment.
 link:../../architecture/core_concepts/pods_and_services.html#proxy-mode[service
 proxy implementation] to use: either *iptables* for the pure-iptables
 version (the default), or *userspace* for the userspace proxy.
+
+|`*openshift_docker_additional_registries*`
+|{product-title} adds the specified additional registry or registries to the
+Docker configuration.
+
+|`*openshift_docker_insecure_registries*`
+|{product-title} adds the specified additional insecure registry or registries
+to the Docker configuration.
+
+|`*openshift_docker_blocked_registries*`
+|{product-title} adds the specified blocked egistry or registries to the Docker
+configuration.
 |===
 
 [[advanced-install-configuring-global-proxy]]