chore: pin RabbitMQ version to avoid inconsistencies

Specifically, this is to avoid having different versions of RabbitMQ
running in different environments, but also to prevent upgrade to 4.x
which is not recommended for OpenStack.

Author: skrobul

components/openstack/templates/openstack-cluster.yaml.tpl

@@ -9,6 +9,7 @@ metadata:
 spec:
   replicas: 3
   persistence: {{ .Values.rabbitmq.persistence | toJson }}
+  image: {{ .Values.rabbitmq.image |  default "rabbitmq:3.13.7-management" }} # renovate:ignore
   affinity:
     nodeAffinity:
       requiredDuringSchedulingIgnoredDuringExecution: