subtests.docker_daemon: Adds tests for connection with certificate.

Tests generates certificates and sign them up with created CA certificate,
then test connect server and client part with different configurations.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
BTW, and not sure if it's still true, but I did find early dockers totally ignore ``/etc/hosts`` content and go straight to the system resolver (meaning you'd have to setup an actual dns server or dns-masq :S).  Hopefully fixed now.