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: Ia9d09515435618624919ad715ffa3df833a50a7a
Closes-Bug: #1628580

manifests/db/sync.pp

@@ -26,6 +26,8 @@ class keystone::db::sync(
     path        => '/usr/bin',
     user        => $keystone_user,
     refreshonly => true,
+    try_sleep   => 5,
+    tries       => 10,
     subscribe   => [
       Anchor['keystone::install::end'],
       Anchor['keystone::config::end'],