Push internal loading back to prepare step

plays/lib/prepare.yml

@@ -1,4 +1,15 @@
 ---
+- name: Check if internal system variables exists
+  stat:
+    path: "{{ plugin_config_root }}/vars.yml"
+  register: vars_yml
+
+- name: Load internal system variables
+  no_log: true
+  when: vars_yml.stat.exists
+  include_vars:
+    file: "{{ plugin_config_root }}/vars.yml"
+
 - name: Export internal variable placeholders
   set_fact:
     dokku_mariadb_db_addr: "dokku-mariadb-{{ app }}"

plays/lib/vars.yml

@@ -1,15 +1,4 @@
 ---
-- name: Check if internal system variables exists
-  stat:
-    path: "{{ plugin_config_root }}/vars.yml"
-  register: vars_yml
-
-- name: Load internal system variables
-  no_log: true
-  when: vars_yml.stat.exists
-  include_vars:
-    file: "{{ plugin_config_root }}/vars.yml"
-
 - name: Check if the app config file exists
   stat:
     path: "{{ app_config_root }}/config.yml"