For some reason we were missing these and that was causing some CPUs to
remain idle, and some boards to have too high load and some tests timing
out occasionally.
Set FDO_CI_CONCURRENT for the number of cores, plus one to account for
GPU and I/O waits.
Reviewed-by: David Heidelberg <david.heidelberg@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18028>
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