Clear message on skipping auto-configuration for packaged installations

[jkakavas]

When we install an RPM/DEB package and we determine that we should not run auto-configuration for security features, we simply print:

--------------------------- Security autoconfiguration information ------------------------------

Skipping auto-configuration because security features appear to be already configured.

-------------------------------------------------------------------------------------------------

This can be misleading and also hides the actual cause of us skipping auto-configuration.

We can add a more generic default message and pass -v to https://github.com/elastic/elasticsearch/blob/master/distribution/packages/src/common/scripts/postinst#L65 so that the actual reason of not doing auto-configuration is printed above this message directly from AutoConfigureNode class.

[elasticmachine]

Pinging @elastic/es-security (Team:Security)