subtests.docker_cli.build: Add two new subtests

This pull request fixes issue https://github.com/autotest/autotest-docker/issues/230. For now I used path to my special git repo hosted on github. It could stay like that or we can create this repo within the autotest namespace. The only requirement for this repo is that the docker files are stored in root.

These subtests use https and git repository as source path for
docker build.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Well, this is one safe location... Do as you want :smile:...