Automatically add generated self-signed certificates to Java trust store

[joschi]

If people are using the automatically generated X.509 certificates for the Graylog REST API, proxy calls to Graylog with OkHttp will fail because those certificates are untrusted. If we added the generated certificate to the Java trust store, at least "local" calls would succeed.

Similar problem: http://docs.graylog.org/en/2.0/pages/faq.html#i-have-configured-an-smtp-server-or-an-output-with-tls-connection-and-receive-handshake-errors-what-should-i-do

https://docs.oracle.com/javase/8/docs/technotes/guides/security/jsse/JSSERefGuide.html#CustomizingStores

[joschi]

The feature is broken beyond repair and should be removed instead: #2355