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/run-devstack/tasks/main.yaml b/roles/run-devstack/tasks/main.yaml
new file mode 100644
index 0000000..bafebaf
--- /dev/null
+++ b/roles/run-devstack/tasks/main.yaml
@@ -0,0 +1,6 @@
+- name: Run devstack
+  command: ./stack.sh
+  args:
+    chdir: "{{devstack_base_dir}}/devstack"
+  become: true
+  become_user: stack