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: I983008e9cdd46f64ee91712c602712d4eed31714
Closes-Bug: #1628580

manifests/db/sync.pp

@@ -21,6 +21,8 @@ class magnum::db::sync(
     path        => '/usr/bin',
     user        => $user,
     refreshonly => true,
+    try_sleep   => 5,
+    tries       => 10,
     logoutput   => on_failure,
   }