include chain and privkey files for tls_config

Summary:
Include more tls options in the example configuration. If you want to
correctly configure your ssl certificate including the intermediate servers
it's important to configure the cacertfile otherwise the chain is omitted in
the ssl response. (tested with openssl s_client).

The documentation should be updated as well.

Reviewers: #guam_developers

Subscribers: seigo

Differential Revision: https://git.kolab.org/D314