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>
Don't be afraid to set these timeouts fairly long.  Maybe it's running on a VM w/o much entropy, I've seen that happen before and stall key generation by **minutes**.  For automated testing, nobody's going to be waiting around for this to finish, but it would be a shame to fail if this hapended to ever take 21-seconds :cry: