subtests.docker_cli: Add test run_cidfile

Fixes: https://github.com/autotest/autotest-docker/issues/264

This test is focussed on correct handling of `docker run --cidfile`

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Maybe I got the wrong method, there's one in there that makes the file and hands you back the name and an open fd.  Then you just close the fd and return the name, assuming nothing else opens/uses that file in the meanwhile.  In any case, like I said, it's just a small thing.  No worries.