subtests.docker_cli.build: Add 2 new variants

Fixes issue https://github.com/autotest/autotest-docker/issues/226 + also utilize the `--no-cache` feature.

_update: It also covers the issue: https://github.com/autotest/autotest-docker/issues/227 _

Those variants test the --rm and --no-cache features.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>

_PS: I'll add `--force-rm` test probably tomorrow..._