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>
I wanted to do it using `NamedTemporaryFile()` but I'd have to create it, remove it and then use only the name. Which seems wrong to me. As `self.tmpdir` is used it should be probably even safe to hardcode the name, but I think this is safer and still simple enough...