Added retries for db_sync

If db sync fails, it is never retried leading to errors. So, this
patch adds retries for db_sync to avoid sync fails.

Change-Id: I00051bf680df897fa039fe63a737c518924f448e
Closes-Bug: #1628580

manifests/db/sync.pp

@@ -25,6 +25,8 @@ class ironic::db::sync(
     # https://bugs.launchpad.net/cloud-archive/+bug/1450942
     user        => 'root',
     refreshonly => true,
+    try_sleep   => 5,
+    tries       => 10,
     logoutput   => on_failure,
     subscribe   => [
       Anchor['ironic::install::end'],