enable additional tests

We hit a situation where the downstream tests behind the RHT firewall caught an issue with the RHCOS compose because we aren't running the same suite of tests upstream. Notably the kola testiso tests.

+ kola testiso -S --qemu-native-4k --qemu-multipath --scenarios iso-install --output-dir tmp/kola-metal4k
Testing scenarios: [iso-install]
Successfully tested scenario pxe-install for 49.84.202106211326-0 on bios (metal)
Successfully tested scenario iso-install for 49.84.202106211326-0 on bios (metal)
Successfully tested scenario iso-offline-install for 49.84.202106211326-0 on bios (metal)
[Pipeline] }
Error: scenario iso-install: timed out after 10m0s
2021-06-21T14:25:48Z cli: scenario iso-install: timed out after 10m0s

In this case, the root cause was a missing patch to Ignition in the 4.9 builds.

In build-test-qemu.sh, there is a TODO about turning on additional tests but there is a want for multiple tiers and splitting them into pods.

https://github.com/openshift/os/blob/38dd8888309f8a43a9163ee9372416e1bddac0b8/ci/build-test-qemu.sh#L26-L28

Are we in a position to try turning on more tests now? Do we need to design how multiple tiers would work? Or are we waiting for a gangplank future?

Start with the TODO in ci/build-test-qemu.sh and compare the upstream test coverage with the cited kola testiso command and its iso-install scenarios. Investigate whether additional tests can be enabled directly or require test tiers and separate pods. Done means an agreed testing approach and enabled coverage that includes the relevant upstream scenarios.