Minor fixes to help integration of CORD-912

Change-Id: I8dd69bf2eae091ca60bbbfbfebce465405662a58
diff --git a/roles/onos-fabric-install/defaults/main.yml b/roles/onos-fabric-install/defaults/main.yml
index 2c70fc8..aaa91e9 100644
--- a/roles/onos-fabric-install/defaults/main.yml
+++ b/roles/onos-fabric-install/defaults/main.yml
@@ -4,7 +4,8 @@
 # paths
 head_onos_fabric_dir: "/opt/onos_fabric"
 
-# Should probably be set to a specific version
-onos_docker_image: "opencord/onos:latest"
-
+# ONOS docker image to use
+deploy_docker_registry: ""
+deploy_docker_tag: "candidate"
+onos_docker_image: "{{ deploy_docker_registry }}onosproject/onos:{{ deploy_docker_tag }}"