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 three lines can be done in a single line with:

    DockerCmd('rm', [self.sub_stuff["cont1_name"]]).execute()