copr-fe: unblock copr-fe playbook

We will have a new variable copr_uptimerobot_api_key_ro soon:
https://pagure.io/fedora-infrastructure/issue/10456

roles/copr/frontend/tasks/main.yml

@@ -192,5 +192,5 @@
     group: "nagios"
     mode: 0750
   vars:
-    api_key: "{{ copr_uptimerobot_api_key_ro }}"
+    api_key: "{{ copr_uptimerobot_api_key_ro | default("not-configured") }}"
   tags: copr_cdn

roles/copr/frontend/templates/copr-cdn-check.py.j2

@@ -68,6 +68,9 @@ class UptimeRobot:
 def main():
     monitor_name = "Copr's CDN"
     uptime_robot = UptimeRobot(API_KEY)
+    if API_KEY == "not-configured":
+        LOG.info(API_KEY)
+        sys.exit(NAG_OK)
 
     monitor = uptime_robot.get_monitor(monitor_name)
     if monitor: