run_once Checking mongodb backend for ceilometer

TrivialFix

Change-Id: I54151df7f869e0a7915ce6361eda8dfefe5d1870

ansible/roles/prechecks/tasks/service_checks.yml

@@ -59,6 +59,7 @@
       or groups['neutron-l3-agent'] | length < 2
 
 - name: Checking mongodb backend for ceilometer
+  run_once: True
   local_action: fail msg="ceilometer_database_type set to 'mongodb' but mongodb is not enabled"
   changed_when: false
   when: