dockertest: Fix reaction to missing subsubtests variable in config.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
dockertest: fix docker daemon to works properly for systemd.

try to stop service.socket to be sure that service will not start.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
docker_daemon: Adds restart tests.

Signed-off-by: Jiří Župka <jzupka@redhat.com>