An HASingletonElectionPolicy impl that allows configurable specification of a "preferred server". If the preferred server is running, it's the master, otherwise the master is deterministically selected based on the standard policy.

1) Determine if you are the preferred server by comparing you node name to the configured "preferred server" value.

2) When you get a view change, check if preferred server is in the view. If yes, and you're the preferred server, become master, otherwise don't. If preferred server is not in view, fall back on the base policy.

Have to make sure the mechanism of identifying and matching the "preferred server" is bullet proof (machine names vs. configuration-specified names vs. IP addresses, plus ports.)