TEST-55-OOMD: workaround for kernel regression in 6.12-rcX

TEST-55-OOMD: workaround for kernel regression in 6.12-rcX

This ignore failures when running on kernel-6.12-rcX, which has a
regression in the kernel scheduler that breaks PSI.

From https://github.com/systemd/systemd/issues/32730#issuecomment-2415312260
> There is a known scheduler bug in 6.12 that breaks psi. It leaks
> "running tasks" counts, which matches your symptoms of seeing partial
> pressure only.
>
> Do you see "inconsistent task state" warnings in dmesg | grep psi?
>
> A fix is queued in the scheduler tree, should be sent to Linus shortly:
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=c6508124193d42bbc3224571eb75bfa4c1821fbb

Workaround for #32730.