Renames the following settings to remove the mention of `zen` in their names:
- `discovery.zen.hosts_provider` -> `discovery.seed_providers`
- `discovery.zen.ping.unicast.concurrent_connects` -> `discovery.seed_resolver.max_concurrent_resolvers`
- `discovery.zen.ping.unicast.hosts.resolve_timeout` -> `discovery.seed_resolver.timeout`
- `discovery.zen.ping.unicast.hosts` -> `discovery.seed_addresses`
Reduces the leader and follower check timeout to 3 * 10 = 30s instead of 3 * 30 = 90s, with 30s still
being a very long time for a node to be completely unresponsive.
David Turner
Yannick Welsch
Lisa Cawley