Scheduled messages not saved to LevelDB backing

If you enable LevelDB storage, scheduled messages do not use LevelDB. They only support KahaDB.

This causes a number of problems:

1. If you're using LevelDB replication, when you failover, ALL scheduled messages are lost.

2. You're still stuck with having KahaDB in your application. If you've made the decision to migrate to LevelDB you're still stuck with Kaha...