Plugins using server.host default 0.0.0.0 broken on Windows

[w33ble]

Kibana binds to 0.0.0.0 by default. This creates an issue for Windows users.

On Unix, 0.0.0.0 is a valid hostname that you can make requests to directly. However, on Windows, that's not true - it binds to any address on the machine, but 0.0.0.0 is not a valid hostname.

So, any part of Kibana, or any plugin, trying to use server.host to craft a request will fail. This is evidenced in Reporting, as reported in #7338

Elasticsearch changed their default binding from 0.0.0.0 to 127.0.0.1 a while back, perhaps we should do the same. It's a simple change and a confirmed fix for this issue.

[jbudz]

Related #7196

[w33ble]

Note that this will be an issue in the 4.x branch as well...

[thomasneirynck]

#7196 has been fixed for 5.X. That change in default would address this issue.

I'm not sure if we want to backport this, since it changes the default behavior. IMO, we assign a 5.X fix version for this, and not backport it.

@w33ble @jbudz @epixa what do you think? we close this as fixed for 5.X, and not backport?

[epixa]

I think you're right. This is a BC break, so it's not something we can backport.

[epixa]

@w33ble If this causes an issue with reporting on windows, then we need to make sure to draw attention to it in the 2.4 reporting docs.

[thomasneirynck]

By changing the default to localhost, this issue is avoided for Windows. Only applies for 5.x and onward (see #8010).