Add var to override hash used for repo setup

The image build playbook, when used for periodic, requires
a different hash to set up repos. This review adds the
var to enable the override.

Change-Id: Ia18962abb58954169a86a0833fee33fcbde81601

playbooks/tripleo-buildimages/pre.yaml

@@ -1,11 +1,20 @@
 - hosts: all
   name: TripleO image building job pre.yaml
-  roles:
-    - role: bindep
-      bindep_dir: "{{ ansible_user_dir }}/{{ zuul.projects['opendev.org/openstack/python-tripleoclient'].src_dir }}"
-    - role: tripleo-repos
-      tripleo_repos_repository: "{{ ansible_user_dir }}/{{ zuul.projects['opendev.org/openstack/tripleo-repos'].src_dir }}"
   tasks:
+
+    - name: Include tripleo-repos
+      include_role:
+          name: tripleo-repos
+      vars:
+        override_repos: "{{ build_override_repos | default('') }}"
+        tripleo_repos_repository: "{{ ansible_user_dir }}/{{ zuul.projects['opendev.org/openstack/tripleo-repos'].src_dir }}"
+
+    - name: Include bindep role
+      include_role:
+        name: bindep
+      vars:
+        bindep_dir: "{{ ansible_user_dir }}/{{ zuul.projects['opendev.org/openstack/python-tripleoclient'].src_dir }}"
+
     - name: Import pre tasks from build-images role
       include_role:
         name: oooci-build-images