Set discovery.seed_hosts: [] even when using file based seed hosts provider

[pebrc]

It is recommended to set discovery.seed_hosts: [] in elasticsearch.yml (static setting) even in the presence of the discovery.seed_providers: file.

The setting has an effect even if the seed provider is file based and relies on unicast_hosts.txt as it is the case with ECK operator managed Elasticsearch clusters.

If left unset and something goes wrong with the master we will get a bunch of noise about being unable to discover nodes at the default address(es) i.e. trying and failing to connect to at least 127.0.0.1:${TRANSPORT_PORT} (paraphrasing @\DaveCTurner here)