Not all distros support booting without an initrd. E.g. the Debian
kernel builds ext4 as a module and so relies on an initrd to
successfully start the QEMU-based images.
We need to specify a full path to the "ip" binary and busybox "ip" has a
slightly different output than the normal ip, and won't show "DOWN".
hence instead ensure that at lest not "UP" is in there.
Since the new option `--network-namespace-path=` of systemd-nspawn
cannot be used together with other network-related options, we need
to add more smoke tests for checking these conditions of options.
This catches errors like "ninja not found", missing programs etc. early,
instead of silently ignoring them and trying to boot a broken VM.
In install_config_files(), allow some distro specific files to be absent
(such as /etc/sysconfig/init).
All test/TEST* but TEST-02-CRYPTSETUP share the same check_result_qemu()
and test_cleanup(), so move them into test_functions and only override
them in TEST-02-CRYPTSETUP.
Also provide a common test_run() which by default assumes that both QEMU
and nspawn tests are run. Particular tests which don't support either
need to explicitly opt out by setting $TEST_NO_{QEMU,NSPAWN}. Do it this
way around to avoid accidentally forgetting to opt in, and to encourage
test authors to at least always support nspawn.
