Replication disconnection tests

These 4 tests set up replication between two appliances, and then temporarily disconnect them to test that replication recovers. Two tests temporarily disable the "database synchronization" role then re-enable it, the other two ssh into the replication parent appliance and stop the DB process itself. These are passing on 5.2.x, but do not yet work on 5.3 due to the latest security changes, and the requirement that a key be copied over to the second appliance in order to configure replication. An upcoming build will make passing those keys to a second appliance easier, and should enable automating the replication configuration on 5.3.x.