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>
These make pylint complain.  I'd rather keep only static stuff as class attributes.  Otherwise these should go into ``stuff``, it's what stuff's for :D  This way too, everything important to the test is gathered in one place, no need to go hunting all over when debugging.