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>
I'm considering dropping inspector from travis and just using our run_pylint instead, near as I can tell there's no way to tune inspector for our needs: Don't check unittests and use different exclusions for tests vs other code.    Either way, I made an effort to strip out those above comment lines from all tests, so it doesn't make sense to add them back in :)