subtests.docker_cli: Update the structure to allow multiple builds

Update the structure to allow easily to call and verify multiple
builds. Also add couple of new checks and improve cleanup to delete
only non-previously-existing containers/images.

NOTE: It's impossible to cleanup based on the build log because it
doesn't list all used containers (only some of them)

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
subtests.docker_cli.build: Add 2 new variants

Those variants test the --rm and --no-cache features.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
subtests.docker_cli.build: Use local busybox if available

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
subtests.docker_cli: Add 3 variants with bad Dockerfile

This extension covers `docker build` with `-q`, `--force-rm` and
the behavior when the build fails.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Merge pull request #296 from ldoktor/build

subtests.docker_cli.build: Add 2 new variants