Add release pipeline

Similar to [1], this catches tag events.

[1] https://github.com/ansible/project-config/blob/master/zuul.d/pipelines.yaml#L132

Change-Id: Ib96b5e9066fe466a8be29a582ab7bc3ff3b9bf44

zuul.d/pipelines.yaml

@@ -126,3 +126,21 @@
     failure:
       gerrit: {}
       mysql:
+
+- pipeline:
+    name: release
+    description: This pipeline runs in response to any tag event
+    manager: independent
+    precedence: high
+    post-review: True
+    trigger:
+      gerrit:
+        - event: ref-updated
+          ref: ^refs/tags/.*$
+      github:
+        - event: push
+          ref: ^refs/tags/.*$
+    success:
+      mysql:
+    failure:
+      mysql: