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).
If the "systemctl start" happens at an "unlucky" time such as 1000.9 seconds
and then e. g. runs for 2.6 s (sleep 2 plus the overhead of starting the unit
and waiting for it) the END_SEC would be 1003.5s which would round to 1004,
making the difference 4. On busier testbeds the overhead apparently can take a
bit more than 0.5s. The main point is really that it doesn't wait that much
longer, so "-le 4" seems perfectly fine. We allow up to 1.5s in the subsequent
"wait5fail" test below too.
Fixes#4582
Add a test case for job merging with --ignore-dependencies.
test.sh is copied from TEST-01-*, only lightly modified (this
should be refactored better in the future).
test-jobs.sh is the core of this test.
