Re-generate certificates

[octonato]

The current self-signed certificates expired on 14 August 2017.

The certificate is not trusted because the issuer certificate is unknown. The server
might not be sending the appropriate intermediate certificates. An additional root
certificate may need to be imported. The certificate expired on 14 August 2017, 
00:37:51 GMT+2. The current time is 22 November 2018, 20:59. Error code:
SEC_ERROR_UNKNOWN_ISSUER

We should re-generated them.

[wsargent]

The scripts are kind of a pain in the butt.

It may be better to replace them with a single builder that creates key stores / trust stores from https://github.com/tersesystems/securitybuilder or using the SSLConfig FakeKeyStore set.

[octonato]

Yes, indeed. I will have a look on your suggestion.

Thanks @wsargent

[ignasi35]

+1 to using FakeKeyStore more.

Anything we improve in this sample to create certificates on the fly could eventually be picked up by akka-grpc samples apps too.