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`
This commit adds a new QA sub project to the discovery-ec2 plugin.
This project uses a fixture to test the plugin using a multi-node cluster.
Once all nodes are started, the nodes transport addresses are written
in a file that is later read by the fixture.