Create a SQLTest which exercises Dragon snapshot recovery

[purplefox]

Snapshot recovery currently doesn't occur during the normal SQLTest run. We should create a test which triggers this. We don't have full control over when Dragon decides to do this but if we create a test which starts 2 out of 3 nodes then sends a bunch of data before starting the 3rd node, hopefully recovery will occur on the 3rd node.

[purplefox]

Need to verify if this is the case