test: Use Python 3 in check-journal
test: Use Python 3 in check-journal

Python 2 is obsolete in most distributions, so use Python 3 on most
images, except for RHEL/CentOS 7 which don't have Python 3 yet.

In Python 3, `os.kill()` is implemented by `os_kill()`, so factorize the
crashed function name and conditionalize it on the image name.

stefwalter/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,SotolitoLabs/cockpit,martinpitt/cockpit,mvollmer/cockpit,andreasn/cockpit,andreasn/cockpit,cockpituous/cockpit,mvollmer/cockpit,cockpit-project/cockpit,deryni/cockpit,martinpitt/cockpit,cockpituous/cockpit,garrett/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,stefwalter/cockpit,mareklibra/cockpit,mareklibra/cockpit,mareklibra/cockpit,SotolitoLabs/cockpit,deryni/cockpit,cockpituous/cockpit,mareklibra/cockpit,cockpituous/cockpit,andreasn/cockpit,garrett/cockpit,SotolitoLabs/cockpit,moraleslazaro/cockpit,deryni/cockpit,stefwalter/cockpit,SotolitoLabs/cockpit,deryni/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,SotolitoLabs/cockpit,garrett/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpit-project/cockpit,stefwalter/cockpit,deryni/cockpit,stefwalter/cockpit,mvollmer/cockpit,garrett/cockpit,deryni/cockpit,andreasn/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,SotolitoLabs/cockpit,garrett/cockpit,cockpit-project/cockpit,mareklibra/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,mareklibra/cockpit,andreasn/cockpit,stefwalter/cockpit,martinpitt/cockpit,andreasn/cockpit,stefwalter/cockpit,deryni/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,andreasn/cockpit,cockpituous/cockpit