copr: backend: cleanup the redis db periodically

... 10 minutes before other cleanups so the real VMs are actually
terminated automatically.

roles/copr/backend/tasks/main.yml

@@ -288,6 +288,12 @@
         minute="0"
         user=copr
 
+- name: setup crontab for cleaning up redis
+  cron: name="prune redis VM db periodically"
+        job="/usr/local/bin/cleanup-unused-vms-from-redis >> /var/log/copr-backend/cleanup-redis-vms.log"
+        minute="50"
+        user=copr
+
 - name: setup monitoring
   import_tasks: "monitoring.yml"