In the presence of a package-lock.json, `npm install` apparently
downloads all packages even when giving explicit ones on the CLI. Avoid
that by removing package-lock.json before.
So that it can be called from the container-tools module without
duplication. For technical reasons this requires calling the test entry
script from a different directory, so parameterize it.
Rename the test from "browser" to "cockpit-podman" so that it is
more descriptive within a module test.
Drop the TEST_OS hack, tests of current version recognizes RHEL 8.3 just
fine (and in fact depends on it).
Related: rhbz#1821193
