Add galera system level upgrade metadata

Change-Id: I610e290986189704da54a8386d62b4c3b27c8d52
Related-prod: PROD-29630
(cherry picked from commit b8fb87471b1a8e295048ad2036409f1a457d1100)
diff --git a/galera/server/cluster.yml b/galera/server/cluster.yml
index e215910..a4b3f0a 100644
--- a/galera/server/cluster.yml
+++ b/galera/server/cluster.yml
@@ -2,3 +2,4 @@
 - service.haproxy.proxy.single
 - system.haproxy.proxy.listen.openstack.galera
 - system.keepalived.cluster.instance.galera_vip
+- system.galera.upgrade