tests: Run install config and printconfig --all in one test

[cgwalters-bot]

The container integration tests run in parallel under libtest-mimic. printconfig --all writes /run/bootc/install/10-test.toml and removes it when it finishes, while install config runs bootc install print-configuration, which scans that same directory. load_config() lists the fragments first and reads them afterwards. If the file is removed between those two steps, the read fails with Loading configuration: No such file or directory (os error 2). This hit a fork CI run (job log).

The config search path is hardcoded, so the --all test can't use a separate root. Instead, the two checks now run one after the other in a single install config test: first the plain read, then the --all one with the fragment.

Testing was on a 16-core RHEL 10 devspace with the default just build image (centos-stream10, ostree). Each test run was podman run ... bootc-integration-tests container config, which selects just these tests.

• Before the change: 0/1050 failures when run one at a time; the window is only a few microseconds. With 16 copies running at once to load the CPU, there were 3/8000 failures (plus 1/1600 in an earlier pass), each with the error above.
• After the change: 0/8000 failures under the same 16-way load.
• just test-container-integration: 9/9 passed. cargo fmt --check and the Makefile's gating clippy config pass for tests-integration.

It's rare upstream. I searched the logs of every failed job from the last 100 ci.yml runs on bootc-dev/bootc (about 8 days; 28 jobs whose container-test step failed) and found no hits for this error.

bootc requires DCO: the commits have no Signed-off-by, so a maintainer must sign off before merging (e.g. git rebase --signoff <base> and force-push).

Generated-by: https://github.com/cgwalters/#llms

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Review draft in cgwalters-forge, not upstream yet. This section is removed when the PR is opened upstream.

• Upstream: bootc-dev/bootc, base main
• Board item: PVTI_lAHOAQ_SPs4Bj2Gizg8hb8E

To review:

• Approve to open it upstream, ready for review.
• Comment /draft, then approve, to open it upstream as a draft (/ready undoes that).
• Close to drop it.
• Edit the title and description freely: they become the upstream PR's. Review comments are addressed with fixup commits and a reply here.

[cgwalters-bot]

Superseded by #24, which fixes the same race in config loading and also serializes the two tests; closing.

Generated-by: https://github.com/cgwalters/#llms