MongoDB: Improve Docker image vars

Author: owine

roles/mongodb/defaults/main.yml

@@ -33,7 +33,9 @@ mongodb_docker_container: "{{ mongodb_name }}"
 # Image
 mongodb_docker_image_pull: true
 mongodb_docker_image_tag: "6"
-mongodb_docker_image: "mongo:{{ lookup('vars', mongodb_name + '_docker_image_tag', default=mongodb_docker_image_tag) }}"
+mongodb_docker_image_repo: "mongo"
+mongodb_docker_image: "{{ lookup('vars', mongodb_name + '_docker_image_repo', default=mongodb_docker_image_repo)
+                         + ':' + lookup('vars', mongodb_name + '_docker_image_tag', default=mongodb_docker_image_tag) }}"
 
 # Ports
 mongodb_docker_ports_defaults: []