Only set `$SOURCE` to ./source/ if that actually exists, which is when
it is being called through Standard Test Interface.
Provide fallbacks for using FMF [1] or when calling the script manually.
[1] https://github.com/cockpit-project/cockpit-podman/pull/649
Re-use the test skeleton from cockpit. Just run a single integration
test for now, until we make them properly @nondestructive upstream [1].
Run chromium and the test directly on the test bed. For cockpit-podman
tests it's not practical to run them in a cockpit/tasks podman
container, as that container interferes too much with the tests.
[1] https://github.com/cockpit-project/cockpit-podman/pull/356