Add devstack base job for zuul v3

This should be managed in the devstack repo, since it's a base job to
run devstack.

Change-Id: Iffe54fbccbccd68db08f79a1b51dd7f76dbff408
Depends-On: Ie2119f24360d56690ffd772b95a9ea6b98dd4a39
diff --git a/roles/write-devstack-local-conf/tasks/main.yaml b/roles/write-devstack-local-conf/tasks/main.yaml
new file mode 100644
index 0000000..1d67616
--- /dev/null
+++ b/roles/write-devstack-local-conf/tasks/main.yaml
@@ -0,0 +1,9 @@
+- name: Write a job-specific local_conf file
+  become: true
+  become_user: stack
+  devstack_local_conf:
+    path: "{{ devstack_local_conf_path }}"
+    plugins: "{{ devstack_plugins|default(omit) }}"
+    services: "{{ devstack_services|default(omit) }}"
+    localrc: "{{ devstack_localrc|default(omit) }}"
+    local_conf: "{{ devstack_local_conf|default(omit) }}"