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>
That's three times doing the same thing, how about a ``@staticmethod RaiseNA(msg, cmdresult)``?

Ooooo, better yet, just let the cert-generating functions throw exceptions on command-failure.  It's much easier to debug when the traceback points right to the point of failure.  This is key-functionality for the test anyway, so no reason to delay reporting of problems.