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: Ifb01a82e74d3ab46f76d1f94a685e96c86119258
Closes-Bug: #1628580

manifests/db/sync.pp

@@ -16,6 +16,8 @@ class panko::db::sync(
     path        => '/usr/bin',
     user        => 'panko',
     refreshonly => true,
+    try_sleep   => 5,
+    tries       => 10,
     logoutput   => 'on_failure',
   }