Add select

Author: MoteHue

etc/kayobe/kolla/inventory/group_vars/prometheus-blackbox-exporter

@@ -15,7 +15,7 @@ prometheus_blackbox_exporter_endpoints: |
   {% endfor %}
   {% endif %}
   {% endfor %}
-  {{ (endpoints + prometheus_blackbox_exporter_endpoints_custom) | unique | list }}
+  {{ (endpoints + prometheus_blackbox_exporter_endpoints_custom) | unique | select | list }}
 
 # A list of custom prometheus Blackbox exporter endpoints. Each element should
 # have the following format: